diff --git a/internal/telemetry/export/ocagent/metrics.go b/internal/telemetry/export/ocagent/metrics.go
index 11c2a83..6cb824d 100644
--- a/internal/telemetry/export/ocagent/metrics.go
+++ b/internal/telemetry/export/ocagent/metrics.go
@@ -6,6 +6,7 @@
 
 import (
 	"fmt"
+	"time"
 
 	"golang.org/x/tools/internal/telemetry"
 	"golang.org/x/tools/internal/telemetry/export/ocagent/wire"
@@ -95,17 +96,18 @@
 
 // dataToTimeseries returns a slice of *wire.TimeSeries based on the
 // points in data.
-func dataToTimeseries(data telemetry.MetricData) []*wire.TimeSeries {
+func dataToTimeseries(data telemetry.MetricData, start time.Time) []*wire.TimeSeries {
 	if data == nil {
 		return nil
 	}
 
 	numRows := numRows(data)
+	startTimestamp := convertTimestamp(start)
 	timeseries := make([]*wire.TimeSeries, 0, numRows)
 
 	for i := 0; i < numRows; i++ {
 		timeseries = append(timeseries, &wire.TimeSeries{
-			// TODO: attach StartTimestamp
+			StartTimestamp: &startTimestamp,
 			// TODO: labels?
 			Points: dataToPoints(data, i),
 		})
@@ -135,21 +137,23 @@
 func dataToPoints(data telemetry.MetricData, i int) []*wire.Point {
 	switch d := data.(type) {
 	case *metric.Int64Data:
+		timestamp := convertTimestamp(*d.EndTime)
 		return []*wire.Point{
 			{
 				Value: wire.PointInt64Value{
 					Int64Value: d.Rows[i],
 				},
-				// TODO: attach Timestamp
+				Timestamp: &timestamp,
 			},
 		}
 	case *metric.Float64Data:
+		timestamp := convertTimestamp(*d.EndTime)
 		return []*wire.Point{
 			{
 				Value: wire.PointDoubleValue{
 					DoubleValue: d.Rows[i],
 				},
-				// TODO: attach Timestamp
+				Timestamp: &timestamp,
 			},
 		}
 	case *metric.HistogramInt64Data:
@@ -158,10 +162,10 @@
 		for i, val := range d.Info.Buckets {
 			bucketBounds[i] = float64(val)
 		}
-		return distributionToPoints(row.Values, row.Count, float64(row.Sum), bucketBounds)
+		return distributionToPoints(row.Values, row.Count, float64(row.Sum), bucketBounds, *d.EndTime)
 	case *metric.HistogramFloat64Data:
 		row := d.Rows[i]
-		return distributionToPoints(row.Values, row.Count, row.Sum, d.Info.Buckets)
+		return distributionToPoints(row.Values, row.Count, row.Sum, d.Info.Buckets, *d.EndTime)
 	}
 
 	return nil
@@ -170,13 +174,14 @@
 // distributionToPoints returns an array of *wire.Points containing a
 // wire.PointDistributionValue representing a distribution with the
 // supplied counts, count, and sum.
-func distributionToPoints(counts []int64, count int64, sum float64, bucketBounds []float64) []*wire.Point {
+func distributionToPoints(counts []int64, count int64, sum float64, bucketBounds []float64, end time.Time) []*wire.Point {
 	buckets := make([]*wire.Bucket, len(counts))
 	for i := 0; i < len(counts); i++ {
 		buckets[i] = &wire.Bucket{
 			Count: counts[i],
 		}
 	}
+	timestamp := convertTimestamp(end)
 	return []*wire.Point{
 		{
 			Value: wire.PointDistributionValue{
@@ -190,6 +195,7 @@
 					},
 				},
 			},
+			Timestamp: &timestamp,
 		},
 	}
 }
diff --git a/internal/telemetry/export/ocagent/metrics_test.go b/internal/telemetry/export/ocagent/metrics_test.go
index 85e90dd..033a60e 100644
--- a/internal/telemetry/export/ocagent/metrics_test.go
+++ b/internal/telemetry/export/ocagent/metrics_test.go
@@ -3,6 +3,7 @@
 import (
 	"reflect"
 	"testing"
+	"time"
 
 	"golang.org/x/tools/internal/telemetry"
 	"golang.org/x/tools/internal/telemetry/export/ocagent/wire"
@@ -318,14 +319,22 @@
 }
 
 func TestDataToTimeseries(t *testing.T) {
+	epoch := time.Unix(0, 0)
+	epochTimestamp := convertTimestamp(epoch)
+
+	end := time.Unix(30, 0)
+	endTimestamp := convertTimestamp(end)
+
 	tests := []struct {
-		name string
-		data telemetry.MetricData
-		want []*wire.TimeSeries
+		name  string
+		data  telemetry.MetricData
+		start time.Time
+		want  []*wire.TimeSeries
 	}{
 		{
 			"nil data",
 			nil,
+			time.Time{},
 			nil,
 		},
 		{
@@ -336,28 +345,36 @@
 					2,
 					3,
 				},
+				EndTime: &end,
 			},
+			epoch,
 			[]*wire.TimeSeries{
 				&wire.TimeSeries{
 					Points: []*wire.Point{
 						&wire.Point{
-							Value: wire.PointInt64Value{Int64Value: 1},
+							Value:     wire.PointInt64Value{Int64Value: 1},
+							Timestamp: &endTimestamp,
 						},
 					},
+					StartTimestamp: &epochTimestamp,
 				},
 				&wire.TimeSeries{
 					Points: []*wire.Point{
 						&wire.Point{
-							Value: wire.PointInt64Value{Int64Value: 2},
+							Value:     wire.PointInt64Value{Int64Value: 2},
+							Timestamp: &endTimestamp,
 						},
 					},
+					StartTimestamp: &epochTimestamp,
 				},
 				&wire.TimeSeries{
 					Points: []*wire.Point{
 						&wire.Point{
-							Value: wire.PointInt64Value{Int64Value: 3},
+							Value:     wire.PointInt64Value{Int64Value: 3},
+							Timestamp: &endTimestamp,
 						},
 					},
+					StartTimestamp: &epochTimestamp,
 				},
 			},
 		},
@@ -368,21 +385,27 @@
 					1.5,
 					4.5,
 				},
+				EndTime: &end,
 			},
+			epoch,
 			[]*wire.TimeSeries{
 				&wire.TimeSeries{
 					Points: []*wire.Point{
 						&wire.Point{
-							Value: wire.PointDoubleValue{DoubleValue: 1.5},
+							Value:     wire.PointDoubleValue{DoubleValue: 1.5},
+							Timestamp: &endTimestamp,
 						},
 					},
+					StartTimestamp: &epochTimestamp,
 				},
 				&wire.TimeSeries{
 					Points: []*wire.Point{
 						&wire.Point{
-							Value: wire.PointDoubleValue{DoubleValue: 4.5},
+							Value:     wire.PointDoubleValue{DoubleValue: 4.5},
+							Timestamp: &endTimestamp,
 						},
 					},
+					StartTimestamp: &epochTimestamp,
 				},
 			},
 		},
@@ -405,7 +428,9 @@
 						0, 5, 10,
 					},
 				},
+				EndTime: &end,
 			},
+			epoch,
 			[]*wire.TimeSeries{
 				&wire.TimeSeries{
 					Points: []*wire.Point{
@@ -432,8 +457,10 @@
 									},
 								},
 							},
+							Timestamp: &endTimestamp,
 						},
 					},
+					StartTimestamp: &epochTimestamp,
 				},
 			},
 		},
@@ -455,7 +482,9 @@
 						0, 5,
 					},
 				},
+				EndTime: &end,
 			},
+			epoch,
 			[]*wire.TimeSeries{
 				&wire.TimeSeries{
 					Points: []*wire.Point{
@@ -479,8 +508,10 @@
 									},
 								},
 							},
+							Timestamp: &endTimestamp,
 						},
 					},
+					StartTimestamp: &epochTimestamp,
 				},
 			},
 		},
@@ -488,7 +519,7 @@
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got := dataToTimeseries(tt.data)
+			got := dataToTimeseries(tt.data, tt.start)
 			if !reflect.DeepEqual(got, tt.want) {
 				t.Fatalf("Got:\n%s\nWant:\n%s", marshaled(got), marshaled(tt.want))
 			}
@@ -559,11 +590,15 @@
 }
 
 func TestDataToPoints(t *testing.T) {
+	end := time.Unix(30, 0)
+	endTimestamp := convertTimestamp(end)
+
 	int64Data := &metric.Int64Data{
 		Rows: []int64{
 			0,
 			10,
 		},
+		EndTime: &end,
 	}
 
 	float64Data := &metric.Float64Data{
@@ -571,6 +606,7 @@
 			0.5,
 			0.25,
 		},
+		EndTime: &end,
 	}
 
 	histogramInt64Data := &metric.HistogramInt64Data{
@@ -599,6 +635,7 @@
 				0, 5, 10,
 			},
 		},
+		EndTime: &end,
 	}
 
 	histogramFloat64Data := &metric.HistogramFloat64Data{
@@ -627,6 +664,7 @@
 				0, 5, 10,
 			},
 		},
+		EndTime: &end,
 	}
 
 	tests := []struct {
@@ -650,6 +688,7 @@
 					Value: wire.PointInt64Value{
 						Int64Value: 0,
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -662,6 +701,7 @@
 					Value: wire.PointInt64Value{
 						Int64Value: 10,
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -674,6 +714,7 @@
 					Value: wire.PointDoubleValue{
 						DoubleValue: 0.5,
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -686,6 +727,7 @@
 					Value: wire.PointDoubleValue{
 						DoubleValue: 0.25,
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -717,6 +759,7 @@
 							},
 						},
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -748,6 +791,7 @@
 							},
 						},
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -779,6 +823,7 @@
 							},
 						},
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -810,6 +855,7 @@
 							},
 						},
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -826,12 +872,16 @@
 }
 
 func TestDistributionToPoints(t *testing.T) {
+	end := time.Unix(30, 0)
+	endTimestamp := convertTimestamp(end)
+
 	tests := []struct {
 		name    string
 		counts  []int64
 		count   int64
 		sum     float64
 		buckets []float64
+		end     time.Time
 		want    []*wire.Point
 	}{
 		{
@@ -846,6 +896,7 @@
 			buckets: []float64{
 				0, 5, 10,
 			},
+			end: end,
 			want: []*wire.Point{
 				{
 					Value: wire.PointDistributionValue{
@@ -871,6 +922,7 @@
 							},
 						},
 					},
+					Timestamp: &endTimestamp,
 				},
 			},
 		},
@@ -878,7 +930,7 @@
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got := distributionToPoints(tt.counts, tt.count, tt.sum, tt.buckets)
+			got := distributionToPoints(tt.counts, tt.count, tt.sum, tt.buckets, tt.end)
 			if !reflect.DeepEqual(got, tt.want) {
 				t.Fatalf("Got:\n%s\nWant:\n%s", marshaled(got), marshaled(tt.want))
 			}
diff --git a/internal/telemetry/export/ocagent/ocagent.go b/internal/telemetry/export/ocagent/ocagent.go
index d1ebfd2..cad7e13 100644
--- a/internal/telemetry/export/ocagent/ocagent.go
+++ b/internal/telemetry/export/ocagent/ocagent.go
@@ -114,7 +114,7 @@
 func (e *exporter) Metric(ctx context.Context, data telemetry.MetricData) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
-	e.metrics = append(e.metrics, convertMetric(data))
+	e.metrics = append(e.metrics, convertMetric(data, e.config.Start))
 }
 
 func (e *exporter) Flush() {
@@ -202,9 +202,9 @@
 	return result
 }
 
-func convertMetric(data telemetry.MetricData) *wire.Metric {
+func convertMetric(data telemetry.MetricData, start time.Time) *wire.Metric {
 	descriptor := dataToMetricDescriptor(data)
-	timeseries := dataToTimeseries(data)
+	timeseries := dataToTimeseries(data, start)
 
 	if descriptor == nil && timeseries == nil {
 		return nil
diff --git a/internal/telemetry/metric/metric.go b/internal/telemetry/metric/metric.go
index 0333450..98f0bd8 100644
--- a/internal/telemetry/metric/metric.go
+++ b/internal/telemetry/metric/metric.go
@@ -131,6 +131,8 @@
 	IsGauge bool
 	// Rows holds the per group values for the metric.
 	Rows []int64
+	// End is the last time this metric was updated.
+	EndTime *time.Time
 
 	groups []telemetry.TagList
 }
@@ -143,6 +145,8 @@
 	IsGauge bool
 	// Rows holds the per group values for the metric.
 	Rows []float64
+	// End is the last time this metric was updated.
+	EndTime *time.Time
 
 	groups []telemetry.TagList
 }
@@ -153,6 +157,8 @@
 	Info *HistogramInt64
 	// Rows holds the per group values for the metric.
 	Rows []*HistogramInt64Row
+	// End is the last time this metric was updated.
+	EndTime *time.Time
 
 	groups []telemetry.TagList
 }
@@ -177,6 +183,8 @@
 	Info *HistogramFloat64
 	// Rows holds the per group values for the metric.
 	Rows []*HistogramFloat64Row
+	// End is the last time this metric was updated.
+	EndTime *time.Time
 
 	groups []telemetry.TagList
 }
@@ -215,7 +223,7 @@
 func (data *Int64Data) Handle() string              { return data.Info.Name }
 func (data *Int64Data) Groups() []telemetry.TagList { return data.groups }
 
-func (data *Int64Data) modify(ctx context.Context, f func(v int64) int64) {
+func (data *Int64Data) modify(ctx context.Context, at time.Time, f func(v int64) int64) {
 	index, insert := getGroup(ctx, &data.groups, data.Info.Keys)
 	old := data.Rows
 	if insert {
@@ -227,34 +235,31 @@
 		copy(data.Rows, old)
 	}
 	data.Rows[index] = f(data.Rows[index])
+	data.EndTime = &at
 	frozen := *data
 	export.Metric(ctx, &frozen)
 }
 
 func (data *Int64Data) countInt64(ctx context.Context, measure *stats.Int64Measure, value int64, at time.Time) {
-	// TODO: Use at.
-	data.modify(ctx, func(v int64) int64 { return v + 1 })
+	data.modify(ctx, at, func(v int64) int64 { return v + 1 })
 }
 
 func (data *Int64Data) countFloat64(ctx context.Context, measure *stats.Float64Measure, value float64, at time.Time) {
-	// TODO: Use at.
-	data.modify(ctx, func(v int64) int64 { return v + 1 })
+	data.modify(ctx, at, func(v int64) int64 { return v + 1 })
 }
 
 func (data *Int64Data) sum(ctx context.Context, measure *stats.Int64Measure, value int64, at time.Time) {
-	// TODO: Use at.
-	data.modify(ctx, func(v int64) int64 { return v + value })
+	data.modify(ctx, at, func(v int64) int64 { return v + value })
 }
 
 func (data *Int64Data) latest(ctx context.Context, measure *stats.Int64Measure, value int64, at time.Time) {
-	// TODO: Use at.
-	data.modify(ctx, func(v int64) int64 { return value })
+	data.modify(ctx, at, func(v int64) int64 { return value })
 }
 
 func (data *Float64Data) Handle() string              { return data.Info.Name }
 func (data *Float64Data) Groups() []telemetry.TagList { return data.groups }
 
-func (data *Float64Data) modify(ctx context.Context, f func(v float64) float64) {
+func (data *Float64Data) modify(ctx context.Context, at time.Time, f func(v float64) float64) {
 	index, insert := getGroup(ctx, &data.groups, data.Info.Keys)
 	old := data.Rows
 	if insert {
@@ -266,23 +271,23 @@
 		copy(data.Rows, old)
 	}
 	data.Rows[index] = f(data.Rows[index])
+	data.EndTime = &at
 	frozen := *data
 	export.Metric(ctx, &frozen)
 }
 
 func (data *Float64Data) sum(ctx context.Context, measure *stats.Float64Measure, value float64, at time.Time) {
-	data.modify(ctx, func(v float64) float64 { return v + value })
+	data.modify(ctx, at, func(v float64) float64 { return v + value })
 }
 
 func (data *Float64Data) latest(ctx context.Context, measure *stats.Float64Measure, value float64, at time.Time) {
-	// TODO: Use at.
-	data.modify(ctx, func(v float64) float64 { return value })
+	data.modify(ctx, at, func(v float64) float64 { return value })
 }
 
 func (data *HistogramInt64Data) Handle() string              { return data.Info.Name }
 func (data *HistogramInt64Data) Groups() []telemetry.TagList { return data.groups }
 
-func (data *HistogramInt64Data) modify(ctx context.Context, f func(v *HistogramInt64Row)) {
+func (data *HistogramInt64Data) modify(ctx context.Context, at time.Time, f func(v *HistogramInt64Row)) {
 	index, insert := getGroup(ctx, &data.groups, data.Info.Keys)
 	old := data.Rows
 	var v HistogramInt64Row
@@ -300,13 +305,13 @@
 	copy(v.Values, oldValues)
 	f(&v)
 	data.Rows[index] = &v
+	data.EndTime = &at
 	frozen := *data
 	export.Metric(ctx, &frozen)
 }
 
 func (data *HistogramInt64Data) record(ctx context.Context, measure *stats.Int64Measure, value int64, at time.Time) {
-	// TODO: Use at.
-	data.modify(ctx, func(v *HistogramInt64Row) {
+	data.modify(ctx, at, func(v *HistogramInt64Row) {
 		v.Sum += value
 		if v.Min > value || v.Count == 0 {
 			v.Min = value
@@ -326,7 +331,7 @@
 func (data *HistogramFloat64Data) Handle() string              { return data.Info.Name }
 func (data *HistogramFloat64Data) Groups() []telemetry.TagList { return data.groups }
 
-func (data *HistogramFloat64Data) modify(ctx context.Context, f func(v *HistogramFloat64Row)) {
+func (data *HistogramFloat64Data) modify(ctx context.Context, at time.Time, f func(v *HistogramFloat64Row)) {
 	index, insert := getGroup(ctx, &data.groups, data.Info.Keys)
 	old := data.Rows
 	var v HistogramFloat64Row
@@ -344,13 +349,13 @@
 	copy(v.Values, oldValues)
 	f(&v)
 	data.Rows[index] = &v
+	data.EndTime = &at
 	frozen := *data
 	export.Metric(ctx, &frozen)
 }
 
 func (data *HistogramFloat64Data) record(ctx context.Context, measure *stats.Float64Measure, value float64, at time.Time) {
-	// TODO: Use at.
-	data.modify(ctx, func(v *HistogramFloat64Row) {
+	data.modify(ctx, at, func(v *HistogramFloat64Row) {
 		v.Sum += value
 		if v.Min > value || v.Count == 0 {
 			v.Min = value