diff --git a/prometheus.go b/prometheus.go
index 263271d..c33cdef 100644
--- a/prometheus.go
+++ b/prometheus.go
@@ -23,9 +23,11 @@ import (
 	"net/http"
 	"sort"
 	"sync"
+	"time"
 
 	"go.opencensus.io/trace"
 
+	"github.com/golang/protobuf/ptypes"
 	commonpb "github.com/census-instrumentation/opencensus-proto/gen-go/agent/common/v1"
 	metricspb "github.com/census-instrumentation/opencensus-proto/gen-go/metrics/v1"
 	resourcepb "github.com/census-instrumentation/opencensus-proto/gen-go/resource/v1"
@@ -44,10 +46,11 @@ type Exporter struct {
 
 // Options customizes a created Prometheus Exporter.
 type Options struct {
-	Namespace   string
-	OnError     func(err error)
-	ConstLabels prometheus.Labels // ConstLabels will be set as labels on all views.
-	Registry    *prometheus.Registry
+	Namespace      string
+	OnError        func(err error)
+	ConstLabels    prometheus.Labels // ConstLabels will be set as labels on all views.
+	Registry       *prometheus.Registry
+	SendTimestamps bool
 }
 
 // New is the constructor to make an Exporter with the defined Options.
@@ -237,7 +240,7 @@ func (c *collector) protoTimeSeriesToPrometheusMetrics(ctx context.Context, metr
 
 	pmetrics := make([]prometheus.Metric, 0, len(ts.Points))
 	for _, point := range ts.Points {
-		pmet, err := protoMetricToPrometheusMetric(ctx, point, desc, derivedPrometheusValueType, labelValues)
+		pmet, err := protoMetricToPrometheusMetric(ctx, point, desc, derivedPrometheusValueType, labelValues, c.opts.SendTimestamps)
 		if err == nil {
 			pmetrics = append(pmetrics, pmet)
 		} else {
@@ -277,7 +280,12 @@ func protoLabelKeysToLabels(protoLabelKeys []*metricspb.LabelKey) []string {
 	return labelKeys
 }
 
-func protoMetricToPrometheusMetric(ctx context.Context, point *metricspb.Point, desc *prometheus.Desc, derivedPrometheusType prometheus.ValueType, labelValues []string) (prometheus.Metric, error) {
+func protoMetricToPrometheusMetric(ctx context.Context, point *metricspb.Point, desc *prometheus.Desc, derivedPrometheusType prometheus.ValueType, labelValues []string, sendTimestamps bool) (prometheus.Metric, error) {
+	timestamp, err := ptypes.Timestamp(point.Timestamp)
+	if err != nil {
+		timestamp = time.Now()
+	}
+
 	switch value := point.Value.(type) {
 	case *metricspb.Point_DistributionValue:
 		dValue := value.DistributionValue
@@ -308,14 +316,26 @@ func protoMetricToPrometheusMetric(ctx context.Context, point *metricspb.Point,
 			cumCount += countPerBucket
 			points[bucket] = cumCount
 		}
-		return prometheus.NewConstHistogram(desc, uint64(dValue.Count), dValue.Sum, points, labelValues...)
+		metric, err := prometheus.NewConstHistogram(desc, uint64(dValue.Count), dValue.Sum, points, labelValues...)
+		if err != nil || !sendTimestamps {
+			return metric, err
+		}
+		return prometheus.NewMetricWithTimestamp(timestamp, metric), nil
 
 	case *metricspb.Point_Int64Value:
 		// Derive the Prometheus
-		return prometheus.NewConstMetric(desc, derivedPrometheusType, float64(value.Int64Value), labelValues...)
+		metric, err := prometheus.NewConstMetric(desc, derivedPrometheusType, float64(value.Int64Value), labelValues...)
+		if err != nil || !sendTimestamps {
+			return metric, err
+		}
+		return prometheus.NewMetricWithTimestamp(timestamp, metric), nil
 
 	case *metricspb.Point_DoubleValue:
-		return prometheus.NewConstMetric(desc, derivedPrometheusType, value.DoubleValue, labelValues...)
+		metric, err := prometheus.NewConstMetric(desc, derivedPrometheusType, value.DoubleValue, labelValues...)
+		if err != nil || !sendTimestamps {
+			return metric, err
+		}
+		return prometheus.NewMetricWithTimestamp(timestamp, metric), nil
 
 	default:
 		return nil, fmt.Errorf("Unhandled type: %T", point.Value)
diff --git a/prometheus_test.go b/prometheus_test.go
index 6c2d252..47eda01 100644
--- a/prometheus_test.go
+++ b/prometheus_test.go
@@ -39,6 +39,15 @@ var (
 		Seconds: 1543160298,
 		Nanos:   100000997,
 	}
+	// before is a scrape that happened 5s earlier
+	startTimestampBefore = &timestamp.Timestamp{
+		Seconds: 1543160293,
+		Nanos:   100000090,
+	}
+	endTimestampBefore = &timestamp.Timestamp{
+		Seconds: 1543160293,
+		Nanos:   100000997,
+	}
 )
 
 func TestOnlyCumulativeWindowSupported(t *testing.T) {
@@ -303,7 +312,7 @@ func makeMetrics() []*metricspb.Metric {
 			},
 			Timeseries: []*metricspb.TimeSeries{
 				{
-					StartTimestamp: startTimestamp,
+					StartTimestamp: startTimestampBefore,
 					LabelValues: []*metricspb.LabelValue{
 						{Value: "windows"},
 						{Value: "x86"},
@@ -311,7 +320,7 @@ func makeMetrics() []*metricspb.Metric {
 					},
 					Points: []*metricspb.Point{
 						{
-							Timestamp: endTimestamp,
+							Timestamp: endTimestampBefore,
 							Value: &metricspb.Point_Int64Value{
 								Int64Value: 99,
 							},
@@ -319,7 +328,7 @@ func makeMetrics() []*metricspb.Metric {
 					},
 				},
 				{
-					StartTimestamp: startTimestamp,
+					StartTimestamp: startTimestampBefore,
 					LabelValues: []*metricspb.LabelValue{
 						{Value: "darwin"},
 						{Value: "386"},
@@ -327,7 +336,7 @@ func makeMetrics() []*metricspb.Metric {
 					},
 					Points: []*metricspb.Point{
 						{
-							Timestamp: endTimestamp,
+							Timestamp: endTimestampBefore,
 							Value: &metricspb.Point_DoubleValue{
 								DoubleValue: 49.5,
 							},
@@ -443,3 +452,78 @@ with_metric_descriptor_count 2
 		t.Errorf("Mismatched output\nGot:\n%s\nWant:\n%s", g, w)
 	}
 }
+
+func TestMetricsEndpointWithTimestampOutput(t *testing.T) {
+	exp, err := New(Options{
+		SendTimestamps: true,
+	})
+	if err != nil {
+		t.Fatalf("Failed to create Prometheus exporter: %v", err)
+	}
+
+	srv := httptest.NewServer(exp)
+	defer srv.Close()
+
+	// Now record some metrics.
+	metrics := makeMetrics()
+	for _, metric := range metrics {
+		exp.ExportMetric(context.Background(), nil, nil, metric)
+	}
+
+	var i int
+	var output string
+	for {
+		time.Sleep(10 * time.Millisecond)
+		if i == 1000 {
+			t.Fatal("no output at / (10s wait)")
+		}
+		i++
+
+		resp, err := http.Get(srv.URL)
+		if err != nil {
+			t.Fatalf("Failed to get metrics on / error: %v", err)
+		}
+
+		slurp, err := ioutil.ReadAll(resp.Body)
+		_ = resp.Body.Close()
+		if err != nil {
+			t.Fatalf("Failed to read body: %v", err)
+		}
+
+		output = string(slurp)
+		if output != "" {
+			break
+		}
+	}
+
+	if strings.Contains(output, "collected before with the same name and label values") {
+		t.Fatalf("metric name and labels were duplicated but must be unique. Got\n\t%q", output)
+	}
+
+	if strings.Contains(output, "error(s) occurred") {
+		t.Fatalf("error reported by Prometheus registry:\n\t%s", output)
+	}
+
+	want := `# HELP a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_ Unlimited metric key lengths
+# TYPE a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_ counter
+a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_a_{arch="x86",keykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykeykey="",my_org_department="Storage",os="windows"} 99 1543160298100
+# HELP this_one_there_where_ Extra ones
+# TYPE this_one_there_where_ gauge
+this_one_there_where_{arch="386",my_org_department="Ops",os="darwin"} 49.5 1543160293100
+this_one_there_where_{arch="x86",my_org_department="Storage",os="windows"} 99 1543160293100
+# HELP with_metric_descriptor This is a test
+# TYPE with_metric_descriptor histogram
+with_metric_descriptor_bucket{le="0"} 0 1543160298100
+with_metric_descriptor_bucket{le="10"} 1 1543160298100
+with_metric_descriptor_bucket{le="20"} 1 1543160298100
+with_metric_descriptor_bucket{le="30"} 1 1543160298100
+with_metric_descriptor_bucket{le="40"} 6 1543160298100
+with_metric_descriptor_bucket{le="+Inf"} 2 1543160298100
+with_metric_descriptor_sum 61.9 1543160298100
+with_metric_descriptor_count 2 1543160298100
+`
+
+	if g, w := output, want; g != w {
+		t.Errorf("Mismatched output\nGot:\n%s\nWant:\n%s", g, w)
+	}
+}