diff --git a/promql/engine_test.go b/promql/engine_test.go
index 7b7a67a54b..0eff93af4c 100644
--- a/promql/engine_test.go
+++ b/promql/engine_test.go
@@ -3747,12 +3747,12 @@ func TestHistogramRateWithFloatStaleness(t *testing.T) {
 		recoded bool
 	)
 
-	newc, recoded, app, err = app.AppendHistogram(nil, 0, h1.Copy(), false)
+	newc, recoded, app, err = app.AppendHistogram(nil, 0, 0, h1.Copy(), false)
 	require.NoError(t, err)
 	require.False(t, recoded)
 	require.Nil(t, newc)
 
-	newc, recoded, _, err = app.AppendHistogram(nil, 10, h1.Copy(), false)
+	newc, recoded, _, err = app.AppendHistogram(nil, 0, 10, h1.Copy(), false)
 	require.NoError(t, err)
 	require.False(t, recoded)
 	require.Nil(t, newc)
@@ -3762,7 +3762,7 @@ func TestHistogramRateWithFloatStaleness(t *testing.T) {
 	app, err = c2.Appender()
 	require.NoError(t, err)
 
-	app.Append(20, math.Float64frombits(value.StaleNaN))
+	app.Append(0, 20, math.Float64frombits(value.StaleNaN))
 
 	// Make a chunk with two normal histograms that have zero value.
 	h2 := histogram.Histogram{
@@ -3773,12 +3773,12 @@ func TestHistogramRateWithFloatStaleness(t *testing.T) {
 	app, err = c3.Appender()
 	require.NoError(t, err)
 
-	newc, recoded, app, err = app.AppendHistogram(nil, 30, h2.Copy(), false)
+	newc, recoded, app, err = app.AppendHistogram(nil, 0, 30, h2.Copy(), false)
 	require.NoError(t, err)
 	require.False(t, recoded)
 	require.Nil(t, newc)
 
-	newc, recoded, _, err = app.AppendHistogram(nil, 40, h2.Copy(), false)
+	newc, recoded, _, err = app.AppendHistogram(nil, 0, 40, h2.Copy(), false)
 	require.NoError(t, err)
 	require.False(t, recoded)
 	require.Nil(t, newc)
diff --git a/promql/histogram_stats_iterator_test.go b/promql/histogram_stats_iterator_test.go
index cfea8a568e..d3a76820da 100644
--- a/promql/histogram_stats_iterator_test.go
+++ b/promql/histogram_stats_iterator_test.go
@@ -235,4 +235,6 @@ func (h *histogramIterator) AtFloatHistogram(*histogram.FloatHistogram) (int64,
 
 func (*histogramIterator) AtT() int64 { return 0 }
 
+func (*histogramIterator) AtST() int64 { return 0 }
+
 func (*histogramIterator) Err() error { return nil }
diff --git a/promql/value.go b/promql/value.go
index 02cb021024..17afdfc410 100644
--- a/promql/value.go
+++ b/promql/value.go
@@ -487,6 +487,11 @@ func (ssi *storageSeriesIterator) AtT() int64 {
 	return ssi.currT
 }
 
+// TODO(krajorama): implement AtST.
+func (*storageSeriesIterator) AtST() int64 {
+	return 0
+}
+
 func (ssi *storageSeriesIterator) Next() chunkenc.ValueType {
 	if ssi.currH != nil {
 		ssi.iHistograms++
diff --git a/rules/alerting_test.go b/rules/alerting_test.go
index a2c7abcd56..caf32e6472 100644
--- a/rules/alerting_test.go
+++ b/rules/alerting_test.go
@@ -697,12 +697,14 @@ func TestQueryForStateSeries(t *testing.T) {
 		{
 			selectMockFunction: func(bool, *storage.SelectHints, ...*labels.Matcher) storage.SeriesSet {
 				return storage.TestSeriesSet(storage.MockSeries(
+					nil,
 					[]int64{1, 2, 3},
 					[]float64{1, 2, 3},
 					[]string{"__name__", "ALERTS_FOR_STATE", "alertname", "TestRule", "severity", "critical"},
 				))
 			},
 			expectedSeries: storage.MockSeries(
+				nil,
 				[]int64{1, 2, 3},
 				[]float64{1, 2, 3},
 				[]string{"__name__", "ALERTS_FOR_STATE", "alertname", "TestRule", "severity", "critical"},
diff --git a/storage/buffer.go b/storage/buffer.go
index 223c4fa42b..c6a32821d8 100644
--- a/storage/buffer.go
+++ b/storage/buffer.go
@@ -171,6 +171,11 @@ func (s fSample) T() int64 {
 	return s.t
 }
 
+// TODO(krajorama): implement ST.
+func (fSample) ST() int64 {
+	return 0
+}
+
 func (s fSample) F() float64 {
 	return s.f
 }
@@ -200,6 +205,11 @@ func (s hSample) T() int64 {
 	return s.t
 }
 
+// TODO(krajorama): implement ST.
+func (hSample) ST() int64 {
+	return 0
+}
+
 func (hSample) F() float64 {
 	panic("F() called for hSample")
 }
@@ -229,6 +239,11 @@ func (s fhSample) T() int64 {
 	return s.t
 }
 
+// TODO(krajorama): implement ST.
+func (fhSample) ST() int64 {
+	return 0
+}
+
 func (fhSample) F() float64 {
 	panic("F() called for fhSample")
 }
diff --git a/storage/buffer_test.go b/storage/buffer_test.go
index fc6603d4a5..beb9d8e71c 100644
--- a/storage/buffer_test.go
+++ b/storage/buffer_test.go
@@ -402,6 +402,10 @@ func (*mockSeriesIterator) AtT() int64 {
 	return 0 // Not really mocked.
 }
 
+func (*mockSeriesIterator) AtST() int64 {
+	return 0 // Not really mocked.
+}
+
 type fakeSeriesIterator struct {
 	nsamples int64
 	step     int64
@@ -428,6 +432,10 @@ func (it *fakeSeriesIterator) AtT() int64 {
 	return it.idx * it.step
 }
 
+func (*fakeSeriesIterator) AtST() int64 {
+	return 0 // No start timestamps in this fake iterator.
+}
+
 func (it *fakeSeriesIterator) Next() chunkenc.ValueType {
 	it.idx++
 	if it.idx >= it.nsamples {
diff --git a/storage/interface.go b/storage/interface.go
index 23b8b48a0c..a75ac3f58d 100644
--- a/storage/interface.go
+++ b/storage/interface.go
@@ -473,9 +473,10 @@ type Series interface {
 }
 
 type mockSeries struct {
-	timestamps []int64
-	values     []float64
-	labelSet   []string
+	startTimestamps []int64
+	timestamps      []int64
+	values          []float64
+	labelSet        []string
 }
 
 func (s mockSeries) Labels() labels.Labels {
@@ -483,15 +484,19 @@ func (s mockSeries) Labels() labels.Labels {
 }
 
 func (s mockSeries) Iterator(chunkenc.Iterator) chunkenc.Iterator {
-	return chunkenc.MockSeriesIterator(s.timestamps, s.values)
+	return chunkenc.MockSeriesIterator(s.startTimestamps, s.timestamps, s.values)
 }
 
-// MockSeries returns a series with custom timestamps, values and labelSet.
-func MockSeries(timestamps []int64, values []float64, labelSet []string) Series {
+// MockSeries returns a series with custom start timestamp, timestamps, values,
+// and labelSet.
+// Start timestamps is optional, pass nil or empty slice to indicate no start
+// timestamps.
+func MockSeries(startTimestamps, timestamps []int64, values []float64, labelSet []string) Series {
 	return mockSeries{
-		timestamps: timestamps,
-		values:     values,
-		labelSet:   labelSet,
+		startTimestamps: startTimestamps,
+		timestamps:      timestamps,
+		values:          values,
+		labelSet:        labelSet,
 	}
 }
 
diff --git a/storage/interface_test.go b/storage/interface_test.go
index d28e5177e3..3ea4b757e7 100644
--- a/storage/interface_test.go
+++ b/storage/interface_test.go
@@ -23,7 +23,7 @@ import (
 )
 
 func TestMockSeries(t *testing.T) {
-	s := storage.MockSeries([]int64{1, 2, 3}, []float64{1, 2, 3}, []string{"__name__", "foo"})
+	s := storage.MockSeries(nil, []int64{1, 2, 3}, []float64{1, 2, 3}, []string{"__name__", "foo"})
 	it := s.Iterator(nil)
 	ts := []int64{}
 	vs := []float64{}
@@ -35,3 +35,20 @@ func TestMockSeries(t *testing.T) {
 	require.Equal(t, []int64{1, 2, 3}, ts)
 	require.Equal(t, []float64{1, 2, 3}, vs)
 }
+
+func TestMockSeriesWithST(t *testing.T) {
+	s := storage.MockSeries([]int64{0, 1, 2}, []int64{1, 2, 3}, []float64{1, 2, 3}, []string{"__name__", "foo"})
+	it := s.Iterator(nil)
+	ts := []int64{}
+	vs := []float64{}
+	st := []int64{}
+	for it.Next() == chunkenc.ValFloat {
+		t, v := it.At()
+		ts = append(ts, t)
+		vs = append(vs, v)
+		st = append(st, it.AtST())
+	}
+	require.Equal(t, []int64{1, 2, 3}, ts)
+	require.Equal(t, []float64{1, 2, 3}, vs)
+	require.Equal(t, []int64{0, 1, 2}, st)
+}
diff --git a/storage/merge.go b/storage/merge.go
index 12d6d3ac0d..76bf0994e0 100644
--- a/storage/merge.go
+++ b/storage/merge.go
@@ -599,6 +599,13 @@ func (c *chainSampleIterator) AtT() int64 {
 	return c.curr.AtT()
 }
 
+func (c *chainSampleIterator) AtST() int64 {
+	if c.curr == nil {
+		panic("chainSampleIterator.AtST called before first .Next or after .Next returned false.")
+	}
+	return c.curr.AtST()
+}
+
 func (c *chainSampleIterator) Next() chunkenc.ValueType {
 	var (
 		currT           int64
diff --git a/storage/merge_test.go b/storage/merge_test.go
index 6e2daaeb3a..0060950d6f 100644
--- a/storage/merge_test.go
+++ b/storage/merge_test.go
@@ -1716,6 +1716,10 @@ func (errIterator) AtT() int64 {
 	return 0
 }
 
+func (errIterator) AtST() int64 {
+	return 0
+}
+
 func (e errIterator) Err() error {
 	return e.err
 }
diff --git a/storage/remote/codec.go b/storage/remote/codec.go
index 9f0fb7d92a..c689a51164 100644
--- a/storage/remote/codec.go
+++ b/storage/remote/codec.go
@@ -564,6 +564,12 @@ func (c *concreteSeriesIterator) AtT() int64 {
 	return c.series.floats[c.floatsCur].Timestamp
 }
 
+// TODO(krajorama): implement AtST. Maybe. concreteSeriesIterator is used
+// for turning query results into an iterable, but query results do not have ST.
+func (*concreteSeriesIterator) AtST() int64 {
+	return 0
+}
+
 const noTS = int64(math.MaxInt64)
 
 // Next implements chunkenc.Iterator.
@@ -832,6 +838,11 @@ func (it *chunkedSeriesIterator) AtT() int64 {
 	return it.cur.AtT()
 }
 
+// TODO(krajorama): test AtST once we have a chunk format that provides ST.
+func (it *chunkedSeriesIterator) AtST() int64 {
+	return it.cur.AtST()
+}
+
 func (it *chunkedSeriesIterator) Err() error {
 	return it.err
 }
diff --git a/storage/remote/codec_test.go b/storage/remote/codec_test.go
index e6e7813c7b..5da8c8176c 100644
--- a/storage/remote/codec_test.go
+++ b/storage/remote/codec_test.go
@@ -1146,7 +1146,7 @@ func buildTestChunks(t *testing.T) []prompb.Chunk {
 		minTimeMs := time
 
 		for j := range numSamplesPerTestChunk {
-			a.Append(time, float64(i+j))
+			a.Append(0, time, float64(i+j))
 			time += int64(1000)
 		}
 
diff --git a/storage/series.go b/storage/series.go
index 7e130d494d..d114438078 100644
--- a/storage/series.go
+++ b/storage/series.go
@@ -138,6 +138,11 @@ func (it *listSeriesIterator) AtT() int64 {
 	return s.T()
 }
 
+func (it *listSeriesIterator) AtST() int64 {
+	s := it.samples.Get(it.idx)
+	return s.ST()
+}
+
 func (it *listSeriesIterator) Next() chunkenc.ValueType {
 	it.idx++
 	if it.idx >= it.samples.Len() {
@@ -355,18 +360,20 @@ func (s *seriesToChunkEncoder) Iterator(it chunks.Iterator) chunks.Iterator {
 		lastType = typ
 
 		var (
-			t  int64
-			v  float64
-			h  *histogram.Histogram
-			fh *histogram.FloatHistogram
+			st, t int64
+			v     float64
+			h     *histogram.Histogram
+			fh    *histogram.FloatHistogram
 		)
 		switch typ {
 		case chunkenc.ValFloat:
 			t, v = seriesIter.At()
-			app.Append(t, v)
+			st = seriesIter.AtST()
+			app.Append(st, t, v)
 		case chunkenc.ValHistogram:
 			t, h = seriesIter.AtHistogram(nil)
-			newChk, recoded, app, err = app.AppendHistogram(nil, t, h, false)
+			st = seriesIter.AtST()
+			newChk, recoded, app, err = app.AppendHistogram(nil, st, t, h, false)
 			if err != nil {
 				return errChunksIterator{err: err}
 			}
@@ -381,7 +388,8 @@ func (s *seriesToChunkEncoder) Iterator(it chunks.Iterator) chunks.Iterator {
 			}
 		case chunkenc.ValFloatHistogram:
 			t, fh = seriesIter.AtFloatHistogram(nil)
-			newChk, recoded, app, err = app.AppendFloatHistogram(nil, t, fh, false)
+			st = seriesIter.AtST()
+			newChk, recoded, app, err = app.AppendFloatHistogram(nil, st, t, fh, false)
 			if err != nil {
 				return errChunksIterator{err: err}
 			}
diff --git a/tsdb/chunkenc/chunk.go b/tsdb/chunkenc/chunk.go
index fed28c5701..d5e028e681 100644
--- a/tsdb/chunkenc/chunk.go
+++ b/tsdb/chunkenc/chunk.go
@@ -99,9 +99,9 @@ type Iterable interface {
 	Iterator(Iterator) Iterator
 }
 
-// Appender adds sample pairs to a chunk.
+// Appender adds sample with start timestamp, timestamp, and value to a chunk.
 type Appender interface {
-	Append(int64, float64)
+	Append(st, t int64, v float64)
 
 	// AppendHistogram and AppendFloatHistogram append a histogram sample to a histogram or float histogram chunk.
 	// Appending a histogram may require creating a completely new chunk or recoding (changing) the current chunk.
@@ -114,8 +114,8 @@ type Appender interface {
 	// The returned bool isRecoded can be used to distinguish between the new Chunk c being a completely new Chunk
 	// or the current Chunk recoded to a new Chunk.
 	// The Appender app that can be used for the next append is always returned.
-	AppendHistogram(prev *HistogramAppender, t int64, h *histogram.Histogram, appendOnly bool) (c Chunk, isRecoded bool, app Appender, err error)
-	AppendFloatHistogram(prev *FloatHistogramAppender, t int64, h *histogram.FloatHistogram, appendOnly bool) (c Chunk, isRecoded bool, app Appender, err error)
+	AppendHistogram(prev *HistogramAppender, st, t int64, h *histogram.Histogram, appendOnly bool) (c Chunk, isRecoded bool, app Appender, err error)
+	AppendFloatHistogram(prev *FloatHistogramAppender, st, t int64, h *histogram.FloatHistogram, appendOnly bool) (c Chunk, isRecoded bool, app Appender, err error)
 }
 
 // Iterator is a simple iterator that can only get the next value.
@@ -151,6 +151,10 @@ type Iterator interface {
 	// AtT returns the current timestamp.
 	// Before the iterator has advanced, the behaviour is unspecified.
 	AtT() int64
+	// AtST returns the current start timestamp.
+	// Return 0 if the start timestamp is not implemented or not set.
+	// Before the iterator has advanced, the behaviour is unspecified.
+	AtST() int64
 	// Err returns the current error. It should be used only after the
 	// iterator is exhausted, i.e. `Next` or `Seek` have returned ValNone.
 	Err() error
@@ -208,25 +212,30 @@ func (v ValueType) NewChunk() (Chunk, error) {
 	}
 }
 
-// MockSeriesIterator returns an iterator for a mock series with custom timeStamps and values.
-func MockSeriesIterator(timestamps []int64, values []float64) Iterator {
+// MockSeriesIterator returns an iterator for a mock series with custom
+// start timestamp, timestamps, and values.
+// Start timestamps is optional, pass nil or empty slice to indicate no start
+// timestamps.
+func MockSeriesIterator(startTimestamps, timestamps []int64, values []float64) Iterator {
 	return &mockSeriesIterator{
-		timeStamps: timestamps,
-		values:     values,
-		currIndex:  -1,
+		startTimestamps: startTimestamps,
+		timestamps:      timestamps,
+		values:          values,
+		currIndex:       -1,
 	}
 }
 
 type mockSeriesIterator struct {
-	timeStamps []int64
-	values     []float64
-	currIndex  int
+	timestamps      []int64
+	startTimestamps []int64
+	values          []float64
+	currIndex       int
 }
 
 func (*mockSeriesIterator) Seek(int64) ValueType { return ValNone }
 
 func (it *mockSeriesIterator) At() (int64, float64) {
-	return it.timeStamps[it.currIndex], it.values[it.currIndex]
+	return it.timestamps[it.currIndex], it.values[it.currIndex]
 }
 
 func (*mockSeriesIterator) AtHistogram(*histogram.Histogram) (int64, *histogram.Histogram) {
@@ -238,11 +247,18 @@ func (*mockSeriesIterator) AtFloatHistogram(*histogram.FloatHistogram) (int64, *
 }
 
 func (it *mockSeriesIterator) AtT() int64 {
-	return it.timeStamps[it.currIndex]
+	return it.timestamps[it.currIndex]
+}
+
+func (it *mockSeriesIterator) AtST() int64 {
+	if len(it.startTimestamps) == 0 {
+		return 0
+	}
+	return it.startTimestamps[it.currIndex]
 }
 
 func (it *mockSeriesIterator) Next() ValueType {
-	if it.currIndex < len(it.timeStamps)-1 {
+	if it.currIndex < len(it.timestamps)-1 {
 		it.currIndex++
 		return ValFloat
 	}
@@ -268,8 +284,9 @@ func (nopIterator) AtHistogram(*histogram.Histogram) (int64, *histogram.Histogra
 func (nopIterator) AtFloatHistogram(*histogram.FloatHistogram) (int64, *histogram.FloatHistogram) {
 	return math.MinInt64, nil
 }
-func (nopIterator) AtT() int64 { return math.MinInt64 }
-func (nopIterator) Err() error { return nil }
+func (nopIterator) AtT() int64  { return math.MinInt64 }
+func (nopIterator) AtST() int64 { return 0 }
+func (nopIterator) Err() error  { return nil }
 
 // Pool is used to create and reuse chunk references to avoid allocations.
 type Pool interface {
diff --git a/tsdb/chunkenc/chunk_test.go b/tsdb/chunkenc/chunk_test.go
index d2d0e4c053..41bb23ddd1 100644
--- a/tsdb/chunkenc/chunk_test.go
+++ b/tsdb/chunkenc/chunk_test.go
@@ -65,7 +65,7 @@ func testChunk(t *testing.T, c Chunk) {
 			require.NoError(t, err)
 		}
 
-		app.Append(ts, v)
+		app.Append(0, ts, v)
 		exp = append(exp, pair{t: ts, v: v})
 	}
 
@@ -226,7 +226,7 @@ func benchmarkIterator(b *testing.B, newChunk func() Chunk) {
 			if j > 250 {
 				break
 			}
-			a.Append(p.t, p.v)
+			a.Append(0, p.t, p.v)
 			j++
 		}
 	}
@@ -303,7 +303,7 @@ func benchmarkAppender(b *testing.B, deltas func() (int64, float64), newChunk fu
 			b.Fatalf("get appender: %s", err)
 		}
 		for _, p := range exp {
-			a.Append(p.t, p.v)
+			a.Append(0, p.t, p.v)
 		}
 	}
 }
diff --git a/tsdb/chunkenc/float_histogram.go b/tsdb/chunkenc/float_histogram.go
index 797bc596b5..6af2fa68e2 100644
--- a/tsdb/chunkenc/float_histogram.go
+++ b/tsdb/chunkenc/float_histogram.go
@@ -195,7 +195,7 @@ func (a *FloatHistogramAppender) NumSamples() int {
 
 // Append implements Appender. This implementation panics because normal float
 // samples must never be appended to a histogram chunk.
-func (*FloatHistogramAppender) Append(int64, float64) {
+func (*FloatHistogramAppender) Append(int64, int64, float64) {
 	panic("appended a float sample to a histogram chunk")
 }
 
@@ -682,11 +682,11 @@ func (*FloatHistogramAppender) recodeHistogram(
 	}
 }
 
-func (*FloatHistogramAppender) AppendHistogram(*HistogramAppender, int64, *histogram.Histogram, bool) (Chunk, bool, Appender, error) {
+func (*FloatHistogramAppender) AppendHistogram(*HistogramAppender, int64, int64, *histogram.Histogram, bool) (Chunk, bool, Appender, error) {
 	panic("appended a histogram sample to a float histogram chunk")
 }
 
-func (a *FloatHistogramAppender) AppendFloatHistogram(prev *FloatHistogramAppender, t int64, h *histogram.FloatHistogram, appendOnly bool) (Chunk, bool, Appender, error) {
+func (a *FloatHistogramAppender) AppendFloatHistogram(prev *FloatHistogramAppender, _, t int64, h *histogram.FloatHistogram, appendOnly bool) (Chunk, bool, Appender, error) {
 	if a.NumSamples() == 0 {
 		a.appendFloatHistogram(t, h)
 		if h.CounterResetHint == histogram.GaugeType {
@@ -938,6 +938,10 @@ func (it *floatHistogramIterator) AtT() int64 {
 	return it.t
 }
 
+func (*floatHistogramIterator) AtST() int64 {
+	return 0
+}
+
 func (it *floatHistogramIterator) Err() error {
 	return it.err
 }
diff --git a/tsdb/chunkenc/float_histogram_test.go b/tsdb/chunkenc/float_histogram_test.go
index f27de97516..cbeb3171ce 100644
--- a/tsdb/chunkenc/float_histogram_test.go
+++ b/tsdb/chunkenc/float_histogram_test.go
@@ -63,7 +63,7 @@ func TestFirstFloatHistogramExplicitCounterReset(t *testing.T) {
 			chk := NewFloatHistogramChunk()
 			app, err := chk.Appender()
 			require.NoError(t, err)
-			newChk, recoded, newApp, err := app.AppendFloatHistogram(nil, 0, h, false)
+			newChk, recoded, newApp, err := app.AppendFloatHistogram(nil, 0, 0, h, false)
 			require.NoError(t, err)
 			require.Nil(t, newChk)
 			require.False(t, recoded)
@@ -101,7 +101,7 @@ func TestFloatHistogramChunkSameBuckets(t *testing.T) {
 		},
 		NegativeBuckets: []int64{2, 1, -1, -1}, // counts: 2, 3, 2, 1 (total 8)
 	}
-	chk, _, app, err := app.AppendFloatHistogram(nil, ts, h.ToFloat(nil), false)
+	chk, _, app, err := app.AppendFloatHistogram(nil, 0, ts, h.ToFloat(nil), false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	exp = append(exp, floatResult{t: ts, h: h.ToFloat(nil)})
@@ -115,7 +115,7 @@ func TestFloatHistogramChunkSameBuckets(t *testing.T) {
 	h.Sum = 24.4
 	h.PositiveBuckets = []int64{5, -2, 1, -2} // counts: 5, 3, 4, 2 (total 14)
 	h.NegativeBuckets = []int64{4, -1, 1, -1} // counts: 4, 3, 4, 4 (total 15)
-	chk, _, _, err = app.AppendFloatHistogram(nil, ts, h.ToFloat(nil), false)
+	chk, _, _, err = app.AppendFloatHistogram(nil, 0, ts, h.ToFloat(nil), false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	expH := h.ToFloat(nil)
@@ -134,7 +134,7 @@ func TestFloatHistogramChunkSameBuckets(t *testing.T) {
 	h.Sum = 24.4
 	h.PositiveBuckets = []int64{6, 1, -3, 6} // counts: 6, 7, 4, 10 (total 27)
 	h.NegativeBuckets = []int64{5, 1, -2, 3} // counts: 5, 6, 4, 7 (total 22)
-	chk, _, _, err = app.AppendFloatHistogram(nil, ts, h.ToFloat(nil), false)
+	chk, _, _, err = app.AppendFloatHistogram(nil, 0, ts, h.ToFloat(nil), false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	expH = h.ToFloat(nil)
@@ -224,7 +224,7 @@ func TestFloatHistogramChunkBucketChanges(t *testing.T) {
 		NegativeBuckets: []int64{1},
 	}
 
-	chk, _, app, err := app.AppendFloatHistogram(nil, ts1, h1.ToFloat(nil), false)
+	chk, _, app, err := app.AppendFloatHistogram(nil, 0, ts1, h1.ToFloat(nil), false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	require.Equal(t, 1, c.NumSamples())
@@ -260,7 +260,7 @@ func TestFloatHistogramChunkBucketChanges(t *testing.T) {
 	require.True(t, ok) // Only new buckets came in.
 	require.False(t, cr)
 	c, app = hApp.recode(posInterjections, negInterjections, h2.PositiveSpans, h2.NegativeSpans)
-	chk, _, _, err = app.AppendFloatHistogram(nil, ts2, h2.ToFloat(nil), false)
+	chk, _, _, err = app.AppendFloatHistogram(nil, 0, ts2, h2.ToFloat(nil), false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	require.Equal(t, 2, c.NumSamples())
@@ -330,7 +330,7 @@ func TestFloatHistogramChunkAppendable(t *testing.T) {
 
 		ts := int64(1234567890)
 
-		chk, _, app, err := app.AppendFloatHistogram(nil, ts, h.Copy(), false)
+		chk, _, app, err := app.AppendFloatHistogram(nil, 0, ts, h.Copy(), false)
 		require.NoError(t, err)
 		require.Nil(t, chk)
 		require.Equal(t, 1, c.NumSamples())
@@ -557,7 +557,7 @@ func TestFloatHistogramChunkAppendable(t *testing.T) {
 		nextChunk := NewFloatHistogramChunk()
 		app, err := nextChunk.Appender()
 		require.NoError(t, err)
-		newChunk, recoded, newApp, err := app.AppendFloatHistogram(hApp, ts+1, h2, false)
+		newChunk, recoded, newApp, err := app.AppendFloatHistogram(hApp, 0, ts+1, h2, false)
 		require.NoError(t, err)
 		require.Nil(t, newChunk)
 		require.False(t, recoded)
@@ -575,7 +575,7 @@ func TestFloatHistogramChunkAppendable(t *testing.T) {
 		nextChunk := NewFloatHistogramChunk()
 		app, err := nextChunk.Appender()
 		require.NoError(t, err)
-		newChunk, recoded, newApp, err := app.AppendFloatHistogram(hApp, ts+1, h2, false)
+		newChunk, recoded, newApp, err := app.AppendFloatHistogram(hApp, 0, ts+1, h2, false)
 		require.NoError(t, err)
 		require.Nil(t, newChunk)
 		require.False(t, recoded)
@@ -602,7 +602,7 @@ func TestFloatHistogramChunkAppendable(t *testing.T) {
 		nextChunk := NewFloatHistogramChunk()
 		app, err := nextChunk.Appender()
 		require.NoError(t, err)
-		newChunk, recoded, newApp, err := app.AppendFloatHistogram(hApp, ts+1, h2, false)
+		newChunk, recoded, newApp, err := app.AppendFloatHistogram(hApp, 0, ts+1, h2, false)
 		require.NoError(t, err)
 		require.Nil(t, newChunk)
 		require.False(t, recoded)
@@ -717,7 +717,7 @@ func TestFloatHistogramChunkAppendable(t *testing.T) {
 
 func assertNewFloatHistogramChunkOnAppend(t *testing.T, oldChunk Chunk, hApp *FloatHistogramAppender, ts int64, h *histogram.FloatHistogram, expectHeader CounterResetHeader, expectHint histogram.CounterResetHint) {
 	oldChunkBytes := oldChunk.Bytes()
-	newChunk, recoded, newAppender, err := hApp.AppendFloatHistogram(nil, ts, h, false)
+	newChunk, recoded, newAppender, err := hApp.AppendFloatHistogram(nil, 0, ts, h, false)
 	require.Equal(t, oldChunkBytes, oldChunk.Bytes()) // Sanity check that previous chunk is untouched.
 	require.NoError(t, err)
 	require.NotNil(t, newChunk)
@@ -732,7 +732,7 @@ func assertNewFloatHistogramChunkOnAppend(t *testing.T, oldChunk Chunk, hApp *Fl
 
 func assertNoNewFloatHistogramChunkOnAppend(t *testing.T, oldChunk Chunk, hApp *FloatHistogramAppender, ts int64, h *histogram.FloatHistogram, expectHeader CounterResetHeader) {
 	oldChunkBytes := oldChunk.Bytes()
-	newChunk, recoded, newAppender, err := hApp.AppendFloatHistogram(nil, ts, h, false)
+	newChunk, recoded, newAppender, err := hApp.AppendFloatHistogram(nil, 0, ts, h, false)
 	require.Greater(t, len(oldChunk.Bytes()), len(oldChunkBytes)) // Check that current chunk is bigger than previously.
 	require.NoError(t, err)
 	require.Nil(t, newChunk)
@@ -745,7 +745,7 @@ func assertNoNewFloatHistogramChunkOnAppend(t *testing.T, oldChunk Chunk, hApp *
 
 func assertRecodedFloatHistogramChunkOnAppend(t *testing.T, prevChunk Chunk, hApp *FloatHistogramAppender, ts int64, h *histogram.FloatHistogram, expectHeader CounterResetHeader) {
 	prevChunkBytes := prevChunk.Bytes()
-	newChunk, recoded, newAppender, err := hApp.AppendFloatHistogram(nil, ts, h, false)
+	newChunk, recoded, newAppender, err := hApp.AppendFloatHistogram(nil, 0, ts, h, false)
 	require.Equal(t, prevChunkBytes, prevChunk.Bytes()) // Sanity check that previous chunk is untouched. This may change in the future if we implement in-place recoding.
 	require.NoError(t, err)
 	require.NotNil(t, newChunk)
@@ -959,7 +959,7 @@ func TestFloatHistogramChunkAppendableWithEmptySpan(t *testing.T) {
 			require.NoError(t, err)
 			require.Equal(t, 0, c.NumSamples())
 
-			_, _, _, err = app.AppendFloatHistogram(nil, 1, tc.h1, true)
+			_, _, _, err = app.AppendFloatHistogram(nil, 0, 1, tc.h1, true)
 			require.NoError(t, err)
 			require.Equal(t, 1, c.NumSamples())
 			hApp, _ := app.(*FloatHistogramAppender)
@@ -1019,7 +1019,7 @@ func TestFloatHistogramChunkAppendableGauge(t *testing.T) {
 
 		ts := int64(1234567890)
 
-		chk, _, app, err := app.AppendFloatHistogram(nil, ts, h.Copy(), false)
+		chk, _, app, err := app.AppendFloatHistogram(nil, 0, ts, h.Copy(), false)
 		require.NoError(t, err)
 		require.Nil(t, chk)
 		require.Equal(t, 1, c.NumSamples())
@@ -1259,7 +1259,7 @@ func TestFloatHistogramAppendOnlyErrors(t *testing.T) {
 
 		h := tsdbutil.GenerateTestFloatHistogram(0)
 		var isRecoded bool
-		c, isRecoded, app, err = app.AppendFloatHistogram(nil, 1, h, true)
+		c, isRecoded, app, err = app.AppendFloatHistogram(nil, 0, 1, h, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.NoError(t, err)
@@ -1267,7 +1267,7 @@ func TestFloatHistogramAppendOnlyErrors(t *testing.T) {
 		// Add erroring histogram.
 		h2 := h.Copy()
 		h2.Schema++
-		c, isRecoded, _, err = app.AppendFloatHistogram(nil, 2, h2, true)
+		c, isRecoded, _, err = app.AppendFloatHistogram(nil, 0, 2, h2, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.EqualError(t, err, "float histogram schema change")
@@ -1281,7 +1281,7 @@ func TestFloatHistogramAppendOnlyErrors(t *testing.T) {
 
 		h := tsdbutil.GenerateTestFloatHistogram(0)
 		var isRecoded bool
-		c, isRecoded, app, err = app.AppendFloatHistogram(nil, 1, h, true)
+		c, isRecoded, app, err = app.AppendFloatHistogram(nil, 0, 1, h, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.NoError(t, err)
@@ -1289,7 +1289,7 @@ func TestFloatHistogramAppendOnlyErrors(t *testing.T) {
 		// Add erroring histogram.
 		h2 := h.Copy()
 		h2.CounterResetHint = histogram.CounterReset
-		c, isRecoded, _, err = app.AppendFloatHistogram(nil, 2, h2, true)
+		c, isRecoded, _, err = app.AppendFloatHistogram(nil, 0, 2, h2, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.EqualError(t, err, "float histogram counter reset")
@@ -1303,7 +1303,7 @@ func TestFloatHistogramAppendOnlyErrors(t *testing.T) {
 
 		h := tsdbutil.GenerateTestCustomBucketsFloatHistogram(0)
 		var isRecoded bool
-		c, isRecoded, app, err = app.AppendFloatHistogram(nil, 1, h, true)
+		c, isRecoded, app, err = app.AppendFloatHistogram(nil, 0, 1, h, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.NoError(t, err)
@@ -1311,7 +1311,7 @@ func TestFloatHistogramAppendOnlyErrors(t *testing.T) {
 		// Add erroring histogram.
 		h2 := h.Copy()
 		h2.CustomValues = []float64{0, 1, 2, 3, 4, 5, 6, 7}
-		c, isRecoded, _, err = app.AppendFloatHistogram(nil, 2, h2, true)
+		c, isRecoded, _, err = app.AppendFloatHistogram(nil, 0, 2, h2, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.EqualError(t, err, "float histogram counter reset")
@@ -1344,10 +1344,10 @@ func TestFloatHistogramUniqueSpansAfterNext(t *testing.T) {
 	app, err := c.Appender()
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendFloatHistogram(nil, 0, h1, false)
+	_, _, _, err = app.AppendFloatHistogram(nil, 0, 0, h1, false)
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendFloatHistogram(nil, 1, h2, false)
+	_, _, _, err = app.AppendFloatHistogram(nil, 0, 1, h2, false)
 	require.NoError(t, err)
 
 	// Create an iterator and advance to the first histogram.
@@ -1390,10 +1390,10 @@ func TestFloatHistogramUniqueCustomValuesAfterNext(t *testing.T) {
 	app, err := c.Appender()
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendFloatHistogram(nil, 0, h1, false)
+	_, _, _, err = app.AppendFloatHistogram(nil, 0, 0, h1, false)
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendFloatHistogram(nil, 1, h2, false)
+	_, _, _, err = app.AppendFloatHistogram(nil, 0, 1, h2, false)
 	require.NoError(t, err)
 
 	// Create an iterator and advance to the first histogram.
@@ -1435,7 +1435,7 @@ func TestFloatHistogramEmptyBucketsWithGaps(t *testing.T) {
 	c := NewFloatHistogramChunk()
 	app, err := c.Appender()
 	require.NoError(t, err)
-	_, _, _, err = app.AppendFloatHistogram(nil, 1, h1, false)
+	_, _, _, err = app.AppendFloatHistogram(nil, 0, 1, h1, false)
 	require.NoError(t, err)
 
 	h2 := &histogram.FloatHistogram{
@@ -1448,7 +1448,7 @@ func TestFloatHistogramEmptyBucketsWithGaps(t *testing.T) {
 	}
 	require.NoError(t, h2.Validate())
 
-	newC, recoded, _, err := app.AppendFloatHistogram(nil, 2, h2, false)
+	newC, recoded, _, err := app.AppendFloatHistogram(nil, 0, 2, h2, false)
 	require.NoError(t, err)
 	require.True(t, recoded)
 	require.NotNil(t, newC)
@@ -1483,7 +1483,7 @@ func TestFloatHistogramIteratorFailIfSchemaInValid(t *testing.T) {
 			app, err := c.Appender()
 			require.NoError(t, err)
 
-			_, _, _, err = app.AppendFloatHistogram(nil, 1, h, false)
+			_, _, _, err = app.AppendFloatHistogram(nil, 0, 1, h, false)
 			require.NoError(t, err)
 
 			it := c.Iterator(nil)
@@ -1512,7 +1512,7 @@ func TestFloatHistogramIteratorReduceSchema(t *testing.T) {
 			app, err := c.Appender()
 			require.NoError(t, err)
 
-			_, _, _, err = app.AppendFloatHistogram(nil, 1, h, false)
+			_, _, _, err = app.AppendFloatHistogram(nil, 0, 1, h, false)
 			require.NoError(t, err)
 
 			it := c.Iterator(nil)
diff --git a/tsdb/chunkenc/histogram.go b/tsdb/chunkenc/histogram.go
index e05c49c81d..4e77f387d3 100644
--- a/tsdb/chunkenc/histogram.go
+++ b/tsdb/chunkenc/histogram.go
@@ -219,7 +219,7 @@ func (a *HistogramAppender) NumSamples() int {
 
 // Append implements Appender. This implementation panics because normal float
 // samples must never be appended to a histogram chunk.
-func (*HistogramAppender) Append(int64, float64) {
+func (*HistogramAppender) Append(int64, int64, float64) {
 	panic("appended a float sample to a histogram chunk")
 }
 
@@ -734,11 +734,11 @@ func (a *HistogramAppender) writeSumDelta(v float64) {
 	xorWrite(a.b, v, a.sum, &a.leading, &a.trailing)
 }
 
-func (*HistogramAppender) AppendFloatHistogram(*FloatHistogramAppender, int64, *histogram.FloatHistogram, bool) (Chunk, bool, Appender, error) {
+func (*HistogramAppender) AppendFloatHistogram(*FloatHistogramAppender, int64, int64, *histogram.FloatHistogram, bool) (Chunk, bool, Appender, error) {
 	panic("appended a float histogram sample to a histogram chunk")
 }
 
-func (a *HistogramAppender) AppendHistogram(prev *HistogramAppender, t int64, h *histogram.Histogram, appendOnly bool) (Chunk, bool, Appender, error) {
+func (a *HistogramAppender) AppendHistogram(prev *HistogramAppender, _, t int64, h *histogram.Histogram, appendOnly bool) (Chunk, bool, Appender, error) {
 	if a.NumSamples() == 0 {
 		a.appendHistogram(t, h)
 		if h.CounterResetHint == histogram.GaugeType {
@@ -1075,6 +1075,10 @@ func (it *histogramIterator) AtT() int64 {
 	return it.t
 }
 
+func (*histogramIterator) AtST() int64 {
+	return 0
+}
+
 func (it *histogramIterator) Err() error {
 	return it.err
 }
diff --git a/tsdb/chunkenc/histogram_test.go b/tsdb/chunkenc/histogram_test.go
index 38bbd58465..6ac8500e64 100644
--- a/tsdb/chunkenc/histogram_test.go
+++ b/tsdb/chunkenc/histogram_test.go
@@ -64,7 +64,7 @@ func TestFirstHistogramExplicitCounterReset(t *testing.T) {
 			chk := NewHistogramChunk()
 			app, err := chk.Appender()
 			require.NoError(t, err)
-			newChk, recoded, newApp, err := app.AppendHistogram(nil, 0, h, false)
+			newChk, recoded, newApp, err := app.AppendHistogram(nil, 0, 0, h, false)
 			require.NoError(t, err)
 			require.Nil(t, newChk)
 			require.False(t, recoded)
@@ -102,7 +102,7 @@ func TestHistogramChunkSameBuckets(t *testing.T) {
 		},
 		NegativeBuckets: []int64{2, 1, -1, -1}, // counts: 2, 3, 2, 1 (total 8)
 	}
-	chk, _, app, err := app.AppendHistogram(nil, ts, h, false)
+	chk, _, app, err := app.AppendHistogram(nil, 0, ts, h, false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	exp = append(exp, result{t: ts, h: h, fh: h.ToFloat(nil)})
@@ -116,7 +116,7 @@ func TestHistogramChunkSameBuckets(t *testing.T) {
 	h.Sum = 24.4
 	h.PositiveBuckets = []int64{5, -2, 1, -2} // counts: 5, 3, 4, 2 (total 14)
 	h.NegativeBuckets = []int64{4, -1, 1, -1} // counts: 4, 3, 4, 4 (total 15)
-	chk, _, _, err = app.AppendHistogram(nil, ts, h, false)
+	chk, _, _, err = app.AppendHistogram(nil, 0, ts, h, false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	hExp := h.Copy()
@@ -135,7 +135,7 @@ func TestHistogramChunkSameBuckets(t *testing.T) {
 	h.Sum = 24.4
 	h.PositiveBuckets = []int64{6, 1, -3, 6} // counts: 6, 7, 4, 10 (total 27)
 	h.NegativeBuckets = []int64{5, 1, -2, 3} // counts: 5, 6, 4, 7 (total 22)
-	chk, _, _, err = app.AppendHistogram(nil, ts, h, false)
+	chk, _, _, err = app.AppendHistogram(nil, 0, ts, h, false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	hExp = h.Copy()
@@ -235,7 +235,7 @@ func TestHistogramChunkBucketChanges(t *testing.T) {
 		NegativeBuckets: []int64{1},
 	}
 
-	chk, _, app, err := app.AppendHistogram(nil, ts1, h1, false)
+	chk, _, app, err := app.AppendHistogram(nil, 0, ts1, h1, false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 	require.Equal(t, 1, c.NumSamples())
@@ -271,7 +271,7 @@ func TestHistogramChunkBucketChanges(t *testing.T) {
 	require.True(t, ok) // Only new buckets came in.
 	require.Equal(t, NotCounterReset, cr)
 	c, app = hApp.recode(posInterjections, negInterjections, h2.PositiveSpans, h2.NegativeSpans)
-	chk, _, _, err = app.AppendHistogram(nil, ts2, h2, false)
+	chk, _, _, err = app.AppendHistogram(nil, 0, ts2, h2, false)
 	require.NoError(t, err)
 	require.Nil(t, chk)
 
@@ -344,7 +344,7 @@ func TestHistogramChunkAppendable(t *testing.T) {
 
 		ts := int64(1234567890)
 
-		chk, _, app, err := app.AppendHistogram(nil, ts, h.Copy(), false)
+		chk, _, app, err := app.AppendHistogram(nil, 0, ts, h.Copy(), false)
 		require.NoError(t, err)
 		require.Nil(t, chk)
 		require.Equal(t, 1, c.NumSamples())
@@ -581,7 +581,7 @@ func TestHistogramChunkAppendable(t *testing.T) {
 		nextChunk := NewHistogramChunk()
 		app, err := nextChunk.Appender()
 		require.NoError(t, err)
-		newChunk, recoded, newApp, err := app.AppendHistogram(hApp, ts+1, h2, false)
+		newChunk, recoded, newApp, err := app.AppendHistogram(hApp, 0, ts+1, h2, false)
 		require.NoError(t, err)
 		require.Nil(t, newChunk)
 		require.False(t, recoded)
@@ -599,7 +599,7 @@ func TestHistogramChunkAppendable(t *testing.T) {
 		nextChunk := NewHistogramChunk()
 		app, err := nextChunk.Appender()
 		require.NoError(t, err)
-		newChunk, recoded, newApp, err := app.AppendHistogram(hApp, ts+1, h2, false)
+		newChunk, recoded, newApp, err := app.AppendHistogram(hApp, 0, ts+1, h2, false)
 		require.NoError(t, err)
 		require.Nil(t, newChunk)
 		require.False(t, recoded)
@@ -629,7 +629,7 @@ func TestHistogramChunkAppendable(t *testing.T) {
 		nextChunk := NewHistogramChunk()
 		app, err := nextChunk.Appender()
 		require.NoError(t, err)
-		newChunk, recoded, newApp, err := app.AppendHistogram(hApp, ts+1, h2, false)
+		newChunk, recoded, newApp, err := app.AppendHistogram(hApp, 0, ts+1, h2, false)
 		require.NoError(t, err)
 		require.Nil(t, newChunk)
 		require.False(t, recoded)
@@ -776,7 +776,7 @@ func TestHistogramChunkAppendable(t *testing.T) {
 
 func assertNewHistogramChunkOnAppend(t *testing.T, oldChunk Chunk, hApp *HistogramAppender, ts int64, h *histogram.Histogram, expectHeader CounterResetHeader, expectHint histogram.CounterResetHint) {
 	oldChunkBytes := oldChunk.Bytes()
-	newChunk, recoded, newAppender, err := hApp.AppendHistogram(nil, ts, h, false)
+	newChunk, recoded, newAppender, err := hApp.AppendHistogram(nil, 0, ts, h, false)
 	require.Equal(t, oldChunkBytes, oldChunk.Bytes()) // Sanity check that previous chunk is untouched.
 	require.NoError(t, err)
 	require.NotNil(t, newChunk)
@@ -791,7 +791,7 @@ func assertNewHistogramChunkOnAppend(t *testing.T, oldChunk Chunk, hApp *Histogr
 
 func assertNoNewHistogramChunkOnAppend(t *testing.T, currChunk Chunk, hApp *HistogramAppender, ts int64, h *histogram.Histogram, expectHeader CounterResetHeader) {
 	prevChunkBytes := currChunk.Bytes()
-	newChunk, recoded, newAppender, err := hApp.AppendHistogram(nil, ts, h, false)
+	newChunk, recoded, newAppender, err := hApp.AppendHistogram(nil, 0, ts, h, false)
 	require.Greater(t, len(currChunk.Bytes()), len(prevChunkBytes)) // Check that current chunk is bigger than previously.
 	require.NoError(t, err)
 	require.Nil(t, newChunk)
@@ -804,7 +804,7 @@ func assertNoNewHistogramChunkOnAppend(t *testing.T, currChunk Chunk, hApp *Hist
 
 func assertRecodedHistogramChunkOnAppend(t *testing.T, prevChunk Chunk, hApp *HistogramAppender, ts int64, h *histogram.Histogram, expectHeader CounterResetHeader) {
 	prevChunkBytes := prevChunk.Bytes()
-	newChunk, recoded, newAppender, err := hApp.AppendHistogram(nil, ts, h, false)
+	newChunk, recoded, newAppender, err := hApp.AppendHistogram(nil, 0, ts, h, false)
 	require.Equal(t, prevChunkBytes, prevChunk.Bytes()) // Sanity check that previous chunk is untouched. This may change in the future if we implement in-place recoding.
 	require.NoError(t, err)
 	require.NotNil(t, newChunk)
@@ -1029,7 +1029,7 @@ func TestHistogramChunkAppendableWithEmptySpan(t *testing.T) {
 			require.NoError(t, err)
 			require.Equal(t, 0, c.NumSamples())
 
-			_, _, _, err = app.AppendHistogram(nil, 1, tc.h1, true)
+			_, _, _, err = app.AppendHistogram(nil, 1, 0, tc.h1, true)
 			require.NoError(t, err)
 			require.Equal(t, 1, c.NumSamples())
 			hApp, _ := app.(*HistogramAppender)
@@ -1172,7 +1172,7 @@ func TestAtFloatHistogram(t *testing.T) {
 	app, err := chk.Appender()
 	require.NoError(t, err)
 	for i := range input {
-		newc, _, _, err := app.AppendHistogram(nil, int64(i), &input[i], false)
+		newc, _, _, err := app.AppendHistogram(nil, 0, int64(i), &input[i], false)
 		require.NoError(t, err)
 		require.Nil(t, newc)
 	}
@@ -1230,7 +1230,7 @@ func TestHistogramChunkAppendableGauge(t *testing.T) {
 
 		ts := int64(1234567890)
 
-		chk, _, app, err := app.AppendHistogram(nil, ts, h.Copy(), false)
+		chk, _, app, err := app.AppendHistogram(nil, 0, ts, h.Copy(), false)
 		require.NoError(t, err)
 		require.Nil(t, chk)
 		require.Equal(t, 1, c.NumSamples())
@@ -1471,7 +1471,7 @@ func TestHistogramAppendOnlyErrors(t *testing.T) {
 
 		h := tsdbutil.GenerateTestHistogram(0)
 		var isRecoded bool
-		c, isRecoded, app, err = app.AppendHistogram(nil, 1, h, true)
+		c, isRecoded, app, err = app.AppendHistogram(nil, 0, 1, h, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.NoError(t, err)
@@ -1479,7 +1479,7 @@ func TestHistogramAppendOnlyErrors(t *testing.T) {
 		// Add erroring histogram.
 		h2 := h.Copy()
 		h2.Schema++
-		c, isRecoded, _, err = app.AppendHistogram(nil, 2, h2, true)
+		c, isRecoded, _, err = app.AppendHistogram(nil, 0, 2, h2, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.EqualError(t, err, "histogram schema change")
@@ -1493,7 +1493,7 @@ func TestHistogramAppendOnlyErrors(t *testing.T) {
 
 		h := tsdbutil.GenerateTestHistogram(0)
 		var isRecoded bool
-		c, isRecoded, app, err = app.AppendHistogram(nil, 1, h, true)
+		c, isRecoded, app, err = app.AppendHistogram(nil, 0, 1, h, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.NoError(t, err)
@@ -1501,7 +1501,7 @@ func TestHistogramAppendOnlyErrors(t *testing.T) {
 		// Add erroring histogram.
 		h2 := h.Copy()
 		h2.CounterResetHint = histogram.CounterReset
-		c, isRecoded, _, err = app.AppendHistogram(nil, 2, h2, true)
+		c, isRecoded, _, err = app.AppendHistogram(nil, 0, 2, h2, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.EqualError(t, err, "histogram counter reset")
@@ -1515,7 +1515,7 @@ func TestHistogramAppendOnlyErrors(t *testing.T) {
 
 		h := tsdbutil.GenerateTestCustomBucketsHistogram(0)
 		var isRecoded bool
-		c, isRecoded, app, err = app.AppendHistogram(nil, 1, h, true)
+		c, isRecoded, app, err = app.AppendHistogram(nil, 0, 1, h, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.NoError(t, err)
@@ -1523,7 +1523,7 @@ func TestHistogramAppendOnlyErrors(t *testing.T) {
 		// Add erroring histogram.
 		h2 := h.Copy()
 		h2.CustomValues = []float64{0, 1, 2, 3, 4, 5, 6, 7}
-		c, isRecoded, _, err = app.AppendHistogram(nil, 2, h2, true)
+		c, isRecoded, _, err = app.AppendHistogram(nil, 0, 2, h2, true)
 		require.Nil(t, c)
 		require.False(t, isRecoded)
 		require.EqualError(t, err, "histogram counter reset")
@@ -1556,10 +1556,10 @@ func TestHistogramUniqueSpansAfterNextWithAtHistogram(t *testing.T) {
 	app, err := c.Appender()
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 0, h1, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 0, h1, false)
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 1, h2, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 1, h2, false)
 	require.NoError(t, err)
 
 	// Create an iterator and advance to the first histogram.
@@ -1607,10 +1607,10 @@ func TestHistogramUniqueSpansAfterNextWithAtFloatHistogram(t *testing.T) {
 	app, err := c.Appender()
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 0, h1, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 0, h1, false)
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 1, h2, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 1, h2, false)
 	require.NoError(t, err)
 
 	// Create an iterator and advance to the first histogram.
@@ -1653,10 +1653,10 @@ func TestHistogramCustomValuesInternedAfterNextWithAtHistogram(t *testing.T) {
 	app, err := c.Appender()
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 0, h1, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 0, h1, false)
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 1, h2, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 1, h2, false)
 	require.NoError(t, err)
 
 	// Create an iterator and advance to the first histogram.
@@ -1699,10 +1699,10 @@ func TestHistogramCustomValuesInternedAfterNextWithAtFloatHistogram(t *testing.T
 	app, err := c.Appender()
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 0, h1, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 0, h1, false)
 	require.NoError(t, err)
 
-	_, _, _, err = app.AppendHistogram(nil, 1, h2, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 1, h2, false)
 	require.NoError(t, err)
 
 	// Create an iterator and advance to the first histogram.
@@ -1754,7 +1754,7 @@ func BenchmarkAppendable(b *testing.B) {
 		b.Fatal(err)
 	}
 
-	_, _, _, err = app.AppendHistogram(nil, 1, h, true)
+	_, _, _, err = app.AppendHistogram(nil, 0, 1, h, true)
 	if err != nil {
 		b.Fatal(err)
 	}
@@ -1791,7 +1791,7 @@ func TestIntHistogramEmptyBucketsWithGaps(t *testing.T) {
 	c := NewHistogramChunk()
 	app, err := c.Appender()
 	require.NoError(t, err)
-	_, _, _, err = app.AppendHistogram(nil, 1, h1, false)
+	_, _, _, err = app.AppendHistogram(nil, 0, 1, h1, false)
 	require.NoError(t, err)
 
 	h2 := &histogram.Histogram{
@@ -1804,7 +1804,7 @@ func TestIntHistogramEmptyBucketsWithGaps(t *testing.T) {
 	}
 	require.NoError(t, h2.Validate())
 
-	newC, recoded, _, err := app.AppendHistogram(nil, 2, h2, false)
+	newC, recoded, _, err := app.AppendHistogram(nil, 0, 2, h2, false)
 	require.NoError(t, err)
 	require.True(t, recoded)
 	require.NotNil(t, newC)
@@ -1839,7 +1839,7 @@ func TestHistogramIteratorFailIfSchemaInValid(t *testing.T) {
 			app, err := c.Appender()
 			require.NoError(t, err)
 
-			_, _, _, err = app.AppendHistogram(nil, 1, h, false)
+			_, _, _, err = app.AppendHistogram(nil, 0, 1, h, false)
 			require.NoError(t, err)
 
 			it := c.Iterator(nil)
@@ -1868,7 +1868,7 @@ func TestHistogramIteratorReduceSchema(t *testing.T) {
 			app, err := c.Appender()
 			require.NoError(t, err)
 
-			_, _, _, err = app.AppendHistogram(nil, 1, h, false)
+			_, _, _, err = app.AppendHistogram(nil, 0, 1, h, false)
 			require.NoError(t, err)
 
 			it := c.Iterator(nil)
diff --git a/tsdb/chunkenc/xor.go b/tsdb/chunkenc/xor.go
index bbe12a893b..5a9a59dc22 100644
--- a/tsdb/chunkenc/xor.go
+++ b/tsdb/chunkenc/xor.go
@@ -158,7 +158,7 @@ type xorAppender struct {
 	trailing uint8
 }
 
-func (a *xorAppender) Append(t int64, v float64) {
+func (a *xorAppender) Append(_, t int64, v float64) {
 	var tDelta uint64
 	num := binary.BigEndian.Uint16(a.b.bytes())
 	switch num {
@@ -225,11 +225,11 @@ func (a *xorAppender) writeVDelta(v float64) {
 	xorWrite(a.b, v, a.v, &a.leading, &a.trailing)
 }
 
-func (*xorAppender) AppendHistogram(*HistogramAppender, int64, *histogram.Histogram, bool) (Chunk, bool, Appender, error) {
+func (*xorAppender) AppendHistogram(*HistogramAppender, int64, int64, *histogram.Histogram, bool) (Chunk, bool, Appender, error) {
 	panic("appended a histogram sample to a float chunk")
 }
 
-func (*xorAppender) AppendFloatHistogram(*FloatHistogramAppender, int64, *histogram.FloatHistogram, bool) (Chunk, bool, Appender, error) {
+func (*xorAppender) AppendFloatHistogram(*FloatHistogramAppender, int64, int64, *histogram.FloatHistogram, bool) (Chunk, bool, Appender, error) {
 	panic("appended a float histogram sample to a float chunk")
 }
 
@@ -277,6 +277,10 @@ func (it *xorIterator) AtT() int64 {
 	return it.t
 }
 
+func (*xorIterator) AtST() int64 {
+	return 0
+}
+
 func (it *xorIterator) Err() error {
 	return it.err
 }
diff --git a/tsdb/chunkenc/xor_test.go b/tsdb/chunkenc/xor_test.go
index 904e536b49..b30c65283d 100644
--- a/tsdb/chunkenc/xor_test.go
+++ b/tsdb/chunkenc/xor_test.go
@@ -24,7 +24,7 @@ func BenchmarkXorRead(b *testing.B) {
 	app, err := c.Appender()
 	require.NoError(b, err)
 	for i := int64(0); i < 120*1000; i += 1000 {
-		app.Append(i, float64(i)+float64(i)/10+float64(i)/100+float64(i)/1000)
+		app.Append(0, i, float64(i)+float64(i)/10+float64(i)/100+float64(i)/1000)
 	}
 
 	b.ReportAllocs()
diff --git a/tsdb/chunks/chunks.go b/tsdb/chunks/chunks.go
index f8fc9a2e95..ce4c9d3d78 100644
--- a/tsdb/chunks/chunks.go
+++ b/tsdb/chunks/chunks.go
@@ -135,6 +135,7 @@ type Meta struct {
 }
 
 // ChunkFromSamples requires all samples to have the same type.
+// TODO(krajorama): test with ST when chunk formats support it.
 func ChunkFromSamples(s []Sample) (Meta, error) {
 	return ChunkFromSamplesGeneric(SampleSlice(s))
 }
@@ -164,9 +165,9 @@ func ChunkFromSamplesGeneric(s Samples) (Meta, error) {
 	for i := 0; i < s.Len(); i++ {
 		switch sampleType {
 		case chunkenc.ValFloat:
-			ca.Append(s.Get(i).T(), s.Get(i).F())
+			ca.Append(s.Get(i).ST(), s.Get(i).T(), s.Get(i).F())
 		case chunkenc.ValHistogram:
-			newChunk, _, ca, err = ca.AppendHistogram(nil, s.Get(i).T(), s.Get(i).H(), false)
+			newChunk, _, ca, err = ca.AppendHistogram(nil, s.Get(i).ST(), s.Get(i).T(), s.Get(i).H(), false)
 			if err != nil {
 				return emptyChunk, err
 			}
@@ -174,7 +175,7 @@ func ChunkFromSamplesGeneric(s Samples) (Meta, error) {
 				return emptyChunk, errors.New("did not expect to start a second chunk")
 			}
 		case chunkenc.ValFloatHistogram:
-			newChunk, _, ca, err = ca.AppendFloatHistogram(nil, s.Get(i).T(), s.Get(i).FH(), false)
+			newChunk, _, ca, err = ca.AppendFloatHistogram(nil, s.Get(i).ST(), s.Get(i).T(), s.Get(i).FH(), false)
 			if err != nil {
 				return emptyChunk, err
 			}
diff --git a/tsdb/chunks/head_chunks_test.go b/tsdb/chunks/head_chunks_test.go
index 17efd44aa6..c3cbc5a618 100644
--- a/tsdb/chunks/head_chunks_test.go
+++ b/tsdb/chunks/head_chunks_test.go
@@ -559,7 +559,7 @@ func randomChunk(t *testing.T) chunkenc.Chunk {
 	app, err := chunk.Appender()
 	require.NoError(t, err)
 	for range length {
-		app.Append(rand.Int63(), rand.Float64())
+		app.Append(0, rand.Int63(), rand.Float64())
 	}
 	return chunk
 }
diff --git a/tsdb/chunks/samples.go b/tsdb/chunks/samples.go
index 8097bcd72b..280f2dd606 100644
--- a/tsdb/chunks/samples.go
+++ b/tsdb/chunks/samples.go
@@ -25,6 +25,7 @@ type Samples interface {
 
 type Sample interface {
 	T() int64
+	ST() int64
 	F() float64
 	H() *histogram.Histogram
 	FH() *histogram.FloatHistogram
@@ -38,16 +39,20 @@ func (s SampleSlice) Get(i int) Sample { return s[i] }
 func (s SampleSlice) Len() int         { return len(s) }
 
 type sample struct {
-	t  int64
-	f  float64
-	h  *histogram.Histogram
-	fh *histogram.FloatHistogram
+	st, t int64
+	f     float64
+	h     *histogram.Histogram
+	fh    *histogram.FloatHistogram
 }
 
 func (s sample) T() int64 {
 	return s.t
 }
 
+func (s sample) ST() int64 {
+	return s.st
+}
+
 func (s sample) F() float64 {
 	return s.f
 }
diff --git a/tsdb/head.go b/tsdb/head.go
index 955c0ae5a7..213846aa35 100644
--- a/tsdb/head.go
+++ b/tsdb/head.go
@@ -2111,7 +2111,10 @@ func newSample(t int64, v float64, h *histogram.Histogram, fh *histogram.FloatHi
 	return sample{t, v, h, fh}
 }
 
-func (s sample) T() int64                      { return s.t }
+func (s sample) T() int64 { return s.t }
+
+// TODO(krajorama): implement ST.
+func (sample) ST() int64                       { return 0 }
 func (s sample) F() float64                    { return s.f }
 func (s sample) H() *histogram.Histogram       { return s.h }
 func (s sample) FH() *histogram.FloatHistogram { return s.fh }
diff --git a/tsdb/head_append.go b/tsdb/head_append.go
index fceb80bd34..6a04fd16d9 100644
--- a/tsdb/head_append.go
+++ b/tsdb/head_append.go
@@ -1843,7 +1843,8 @@ func (s *memSeries) append(t int64, v float64, appendID uint64, o chunkOpts) (sa
 	if !sampleInOrder {
 		return sampleInOrder, chunkCreated
 	}
-	s.app.Append(t, v)
+	// TODO(krajorama): pass ST.
+	s.app.Append(0, t, v)
 
 	c.maxTime = t
 
@@ -1885,7 +1886,8 @@ func (s *memSeries) appendHistogram(t int64, h *histogram.Histogram, appendID ui
 		prevApp = nil
 	}
 
-	newChunk, recoded, s.app, _ = s.app.AppendHistogram(prevApp, t, h, false) // false=request a new chunk if needed
+	// TODO(krajorama): pass ST.
+	newChunk, recoded, s.app, _ = s.app.AppendHistogram(prevApp, 0, t, h, false) // false=request a new chunk if needed
 
 	s.lastHistogramValue = h
 	s.lastFloatHistogramValue = nil
@@ -1942,7 +1944,8 @@ func (s *memSeries) appendFloatHistogram(t int64, fh *histogram.FloatHistogram,
 		prevApp = nil
 	}
 
-	newChunk, recoded, s.app, _ = s.app.AppendFloatHistogram(prevApp, t, fh, false) // False means request a new chunk if needed.
+	// TODO(krajorama): pass ST.
+	newChunk, recoded, s.app, _ = s.app.AppendFloatHistogram(prevApp, 0, t, fh, false) // False means request a new chunk if needed.
 
 	s.lastHistogramValue = nil
 	s.lastFloatHistogramValue = fh
diff --git a/tsdb/ooo_head.go b/tsdb/ooo_head.go
index c6ae924372..bbb0f10e77 100644
--- a/tsdb/ooo_head.go
+++ b/tsdb/ooo_head.go
@@ -125,7 +125,8 @@ func (o *OOOChunk) ToEncodedChunks(mint, maxt int64) (chks []memChunk, err error
 		}
 		switch encoding {
 		case chunkenc.EncXOR:
-			app.Append(s.t, s.f)
+			// TODO(krajorama): pass ST.
+			app.Append(0, s.t, s.f)
 		case chunkenc.EncHistogram:
 			// Ignoring ok is ok, since we don't want to compare to the wrong previous appender anyway.
 			prevHApp, _ := prevApp.(*chunkenc.HistogramAppender)
@@ -133,7 +134,8 @@ func (o *OOOChunk) ToEncodedChunks(mint, maxt int64) (chks []memChunk, err error
 				newChunk chunkenc.Chunk
 				recoded  bool
 			)
-			newChunk, recoded, app, _ = app.AppendHistogram(prevHApp, s.t, s.h, false)
+			// TODO(krajorama): pass ST.
+			newChunk, recoded, app, _ = app.AppendHistogram(prevHApp, 0, s.t, s.h, false)
 			if newChunk != nil { // A new chunk was allocated.
 				if !recoded {
 					chks = append(chks, memChunk{chunk, cmint, cmaxt, nil})
@@ -148,7 +150,8 @@ func (o *OOOChunk) ToEncodedChunks(mint, maxt int64) (chks []memChunk, err error
 				newChunk chunkenc.Chunk
 				recoded  bool
 			)
-			newChunk, recoded, app, _ = app.AppendFloatHistogram(prevHApp, s.t, s.fh, false)
+			// TODO(krajorama): pass ST.
+			newChunk, recoded, app, _ = app.AppendFloatHistogram(prevHApp, 0, s.t, s.fh, false)
 			if newChunk != nil { // A new chunk was allocated.
 				if !recoded {
 					chks = append(chks, memChunk{chunk, cmint, cmaxt, nil})
diff --git a/tsdb/querier.go b/tsdb/querier.go
index 4a487aa568..ce0292bf24 100644
--- a/tsdb/querier.go
+++ b/tsdb/querier.go
@@ -788,6 +788,11 @@ func (p *populateWithDelSeriesIterator) AtT() int64 {
 	return p.curr.AtT()
 }
 
+// AtST TODO(krajorama): test AtST() when chunks support it.
+func (p *populateWithDelSeriesIterator) AtST() int64 {
+	return p.curr.AtST()
+}
+
 func (p *populateWithDelSeriesIterator) Err() error {
 	if err := p.populateWithDelGenericSeriesIterator.Err(); err != nil {
 		return err
@@ -862,6 +867,7 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 
 // populateCurrForSingleChunk sets the fields within p.currMetaWithChunk. This
 // should be called if the samples in p.currDelIter only form one chunk.
+// TODO(krajorama): test ST when chunks support it.
 func (p *populateWithDelChunkSeriesIterator) populateCurrForSingleChunk() bool {
 	valueType := p.currDelIter.Next()
 	if valueType == chunkenc.ValNone {
@@ -877,7 +883,7 @@ func (p *populateWithDelChunkSeriesIterator) populateCurrForSingleChunk() bool {
 	var (
 		newChunk chunkenc.Chunk
 		app      chunkenc.Appender
-		t        int64
+		st, t    int64
 		err      error
 	)
 	switch valueType {
@@ -893,7 +899,8 @@ func (p *populateWithDelChunkSeriesIterator) populateCurrForSingleChunk() bool {
 			}
 			var h *histogram.Histogram
 			t, h = p.currDelIter.AtHistogram(nil)
-			_, _, app, err = app.AppendHistogram(nil, t, h, true)
+			st = p.currDelIter.AtST()
+			_, _, app, err = app.AppendHistogram(nil, st, t, h, true)
 			if err != nil {
 				break
 			}
@@ -910,7 +917,8 @@ func (p *populateWithDelChunkSeriesIterator) populateCurrForSingleChunk() bool {
 			}
 			var v float64
 			t, v = p.currDelIter.At()
-			app.Append(t, v)
+			st = p.currDelIter.AtST()
+			app.Append(st, t, v)
 		}
 	case chunkenc.ValFloatHistogram:
 		newChunk = chunkenc.NewFloatHistogramChunk()
@@ -924,7 +932,8 @@ func (p *populateWithDelChunkSeriesIterator) populateCurrForSingleChunk() bool {
 			}
 			var h *histogram.FloatHistogram
 			t, h = p.currDelIter.AtFloatHistogram(nil)
-			_, _, app, err = app.AppendFloatHistogram(nil, t, h, true)
+			st = p.currDelIter.AtST()
+			_, _, app, err = app.AppendFloatHistogram(nil, st, t, h, true)
 			if err != nil {
 				break
 			}
@@ -950,6 +959,7 @@ func (p *populateWithDelChunkSeriesIterator) populateCurrForSingleChunk() bool {
 // populateChunksFromIterable reads the samples from currDelIter to create
 // chunks for chunksFromIterable. It also sets p.currMetaWithChunk to the first
 // chunk.
+// TODO(krajorama): test ST when chunks support it.
 func (p *populateWithDelChunkSeriesIterator) populateChunksFromIterable() bool {
 	p.chunksFromIterable = p.chunksFromIterable[:0]
 	p.chunksFromIterableIdx = -1
@@ -965,7 +975,7 @@ func (p *populateWithDelChunkSeriesIterator) populateChunksFromIterable() bool {
 
 	var (
 		// t is the timestamp for the current sample.
-		t     int64
+		st, t int64
 		cmint int64
 		cmaxt int64
 
@@ -1004,23 +1014,26 @@ func (p *populateWithDelChunkSeriesIterator) populateChunksFromIterable() bool {
 			{
 				var v float64
 				t, v = p.currDelIter.At()
-				app.Append(t, v)
+				st = p.currDelIter.AtST()
+				app.Append(st, t, v)
 			}
 		case chunkenc.ValHistogram:
 			{
 				var v *histogram.Histogram
 				t, v = p.currDelIter.AtHistogram(nil)
+				st = p.currDelIter.AtST()
 				// No need to set prevApp as AppendHistogram will set the
 				// counter reset header for the appender that's returned.
-				newChunk, recoded, app, err = app.AppendHistogram(nil, t, v, false)
+				newChunk, recoded, app, err = app.AppendHistogram(nil, st, t, v, false)
 			}
 		case chunkenc.ValFloatHistogram:
 			{
 				var v *histogram.FloatHistogram
 				t, v = p.currDelIter.AtFloatHistogram(nil)
+				st = p.currDelIter.AtST()
 				// No need to set prevApp as AppendHistogram will set the
 				// counter reset header for the appender that's returned.
-				newChunk, recoded, app, err = app.AppendFloatHistogram(nil, t, v, false)
+				newChunk, recoded, app, err = app.AppendFloatHistogram(nil, st, t, v, false)
 			}
 		}
 
@@ -1202,6 +1215,11 @@ func (it *DeletedIterator) AtT() int64 {
 	return it.Iter.AtT()
 }
 
+// AtST TODO(krajorama): test AtST() when chunks support it.
+func (it *DeletedIterator) AtST() int64 {
+	return it.Iter.AtST()
+}
+
 func (it *DeletedIterator) Seek(t int64) chunkenc.ValueType {
 	if it.Iter.Err() != nil {
 		return chunkenc.ValNone
diff --git a/tsdb/querier_test.go b/tsdb/querier_test.go
index 6933aa617a..57a53c46fe 100644
--- a/tsdb/querier_test.go
+++ b/tsdb/querier_test.go
@@ -141,7 +141,7 @@ func createIdxChkReaders(t *testing.T, tc []seriesSamples) (IndexReader, ChunkRe
 				app, _ := chunk.Appender()
 				for _, smpl := range chk {
 					require.NotNil(t, smpl.fh, "chunk can only contain one type of sample")
-					_, _, _, err := app.AppendFloatHistogram(nil, smpl.t, smpl.fh, true)
+					_, _, _, err := app.AppendFloatHistogram(nil, 0, smpl.t, smpl.fh, true)
 					require.NoError(t, err, "chunk should be appendable")
 				}
 				chkReader[chunkRef] = chunk
@@ -150,7 +150,7 @@ func createIdxChkReaders(t *testing.T, tc []seriesSamples) (IndexReader, ChunkRe
 				app, _ := chunk.Appender()
 				for _, smpl := range chk {
 					require.NotNil(t, smpl.h, "chunk can only contain one type of sample")
-					_, _, _, err := app.AppendHistogram(nil, smpl.t, smpl.h, true)
+					_, _, _, err := app.AppendHistogram(nil, 0, smpl.t, smpl.h, true)
 					require.NoError(t, err, "chunk should be appendable")
 				}
 				chkReader[chunkRef] = chunk
@@ -160,7 +160,7 @@ func createIdxChkReaders(t *testing.T, tc []seriesSamples) (IndexReader, ChunkRe
 				for _, smpl := range chk {
 					require.Nil(t, smpl.h, "chunk can only contain one type of sample")
 					require.Nil(t, smpl.fh, "chunk can only contain one type of sample")
-					app.Append(smpl.t, smpl.f)
+					app.Append(0, smpl.t, smpl.f)
 				}
 				chkReader[chunkRef] = chunk
 			}
@@ -790,6 +790,10 @@ func (it *mockSampleIterator) AtT() int64 {
 	return it.s[it.idx].T()
 }
 
+func (it *mockSampleIterator) AtST() int64 {
+	return it.s[it.idx].ST()
+}
+
 func (it *mockSampleIterator) Next() chunkenc.ValueType {
 	if it.idx < len(it.s)-1 {
 		it.idx++
@@ -2096,7 +2100,7 @@ func TestDeletedIterator(t *testing.T) {
 	for i := range 1000 {
 		act[i].t = int64(i)
 		act[i].f = rand.Float64()
-		app.Append(act[i].t, act[i].f)
+		app.Append(0, act[i].t, act[i].f)
 	}
 
 	cases := []struct {
@@ -2156,7 +2160,7 @@ func TestDeletedIterator_WithSeek(t *testing.T) {
 	for i := range 1000 {
 		act[i].t = int64(i)
 		act[i].f = float64(i)
-		app.Append(act[i].t, act[i].f)
+		app.Append(0, act[i].t, act[i].f)
 	}
 
 	cases := []struct {