diff --git a/src/Prometheus/CollectorRegistry.php b/src/Prometheus/CollectorRegistry.php
index a90a4272..2cc52255 100644
--- a/src/Prometheus/CollectorRegistry.php
+++ b/src/Prometheus/CollectorRegistry.php
@@ -206,7 +206,8 @@ public function registerHistogram(
         string $name,
         string $help,
         array $labels = [],
-        array $buckets = null
+        array $buckets = null,
+        ?int $timestamp = null
     ): Histogram {
         $metricIdentifier = self::metricIdentifier($namespace, $name);
         if (isset($this->histograms[$metricIdentifier])) {
@@ -218,7 +219,8 @@ public function registerHistogram(
             $name,
             $help,
             $labels,
-            $buckets
+            $buckets,
+            $timestamp
         );
         return $this->histograms[$metricIdentifier];
     }
@@ -254,12 +256,13 @@ public function getOrRegisterHistogram(
         string $name,
         string $help,
         array $labels = [],
-        array $buckets = null
+        array $buckets = null,
+        ?int $timestamp = null
     ): Histogram {
         try {
             $histogram = $this->getHistogram($namespace, $name);
         } catch (MetricNotFoundException $e) {
-            $histogram = $this->registerHistogram($namespace, $name, $help, $labels, $buckets);
+            $histogram = $this->registerHistogram($namespace, $name, $help, $labels, $buckets, $timestamp);
         }
         return $histogram;
     }
diff --git a/src/Prometheus/Counter.php b/src/Prometheus/Counter.php
index 6fa20022..9795f3a3 100644
--- a/src/Prometheus/Counter.php
+++ b/src/Prometheus/Counter.php
@@ -21,16 +21,16 @@ public function getType(): string
     /**
      * @param string[] $labels e.g. ['status', 'opcode']
      */
-    public function inc(array $labels = []): void
+    public function inc(array $labels = [], ?int $timestamp = null): void
     {
-        $this->incBy(1, $labels);
+        $this->incBy(1, $labels, $timestamp);
     }
 
     /**
      * @param int|float $count e.g. 2
      * @param mixed[] $labels e.g. ['status', 'opcode']
      */
-    public function incBy($count, array $labels = []): void
+    public function incBy($count, array $labels = [], ?int $timestamp = null): void
     {
         $this->assertLabelsAreDefinedCorrectly($labels);
 
@@ -41,6 +41,7 @@ public function incBy($count, array $labels = []): void
                 'type' => $this->getType(),
                 'labelNames' => $this->getLabelNames(),
                 'labelValues' => $labels,
+                'timestamp'   => $timestamp,
                 'value' => $count,
                 'command' => is_float($count) ? Adapter::COMMAND_INCREMENT_FLOAT : Adapter::COMMAND_INCREMENT_INTEGER,
             ]
diff --git a/src/Prometheus/Gauge.php b/src/Prometheus/Gauge.php
index 527aed12..3a5f64b7 100644
--- a/src/Prometheus/Gauge.php
+++ b/src/Prometheus/Gauge.php
@@ -14,7 +14,7 @@ class Gauge extends Collector
      * @param double $value e.g. 123
      * @param string[] $labels e.g. ['status', 'opcode']
      */
-    public function set(float $value, array $labels = []): void
+    public function set(float $value, array $labels = [], ?int $timestamp = null): void
     {
         $this->assertLabelsAreDefinedCorrectly($labels);
 
@@ -26,6 +26,7 @@ public function set(float $value, array $labels = []): void
                 'labelNames' => $this->getLabelNames(),
                 'labelValues' => $labels,
                 'value' => $value,
+                'timestamp' => $timestamp,
                 'command' => Adapter::COMMAND_SET,
             ]
         );
@@ -42,16 +43,16 @@ public function getType(): string
     /**
      * @param string[] $labels
      */
-    public function inc(array $labels = []): void
+    public function inc(array $labels = [], ?int $timestamp = null): void
     {
-        $this->incBy(1, $labels);
+        $this->incBy(1, $labels, $timestamp);
     }
 
     /**
      * @param int|float $value
      * @param string[] $labels
      */
-    public function incBy($value, array $labels = []): void
+    public function incBy($value, array $labels = [], ?int $timestamp = null): void
     {
         $this->assertLabelsAreDefinedCorrectly($labels);
 
@@ -62,6 +63,7 @@ public function incBy($value, array $labels = []): void
                 'type' => $this->getType(),
                 'labelNames' => $this->getLabelNames(),
                 'labelValues' => $labels,
+                'timestamp'   => $timestamp,
                 'value' => $value,
                 'command' => Adapter::COMMAND_INCREMENT_FLOAT,
             ]
diff --git a/src/Prometheus/RegistryInterface.php b/src/Prometheus/RegistryInterface.php
index 4427fff2..ee4c38bc 100644
--- a/src/Prometheus/RegistryInterface.php
+++ b/src/Prometheus/RegistryInterface.php
@@ -111,5 +111,5 @@ public function getHistogram(string $namespace, string $name): Histogram;
      * @return Histogram
      * @throws MetricsRegistrationException
      */
-    public function getOrRegisterHistogram(string $namespace, string $name, string $help, array $labels = [], array $buckets = null): Histogram;
+    public function getOrRegisterHistogram(string $namespace, string $name, string $help, array $labels = [], array $buckets = null, ?int $timestamp = null): Histogram;
 }
diff --git a/src/Prometheus/RenderTextFormat.php b/src/Prometheus/RenderTextFormat.php
index dfc5151a..263608c8 100644
--- a/src/Prometheus/RenderTextFormat.php
+++ b/src/Prometheus/RenderTextFormat.php
@@ -37,11 +37,13 @@ public function render(array $metrics): string
     private function renderSample(MetricFamilySamples $metric, Sample $sample): string
     {
         $labelNames = $metric->getLabelNames();
+        $timestamp = $sample->getTimestamp();
+        $timestampPart = $timestamp === null ? '' : ' ' . $timestamp;
         if ($metric->hasLabelNames() || $sample->hasLabelNames()) {
             $escapedLabels = $this->escapeAllLabels($labelNames, $sample);
-            return $sample->getName() . '{' . implode(',', $escapedLabels) . '} ' . $sample->getValue();
+            return $sample->getName() . '{' . implode(',', $escapedLabels) . '} ' . $sample->getValue() . $timestampPart;
         }
-        return $sample->getName() . ' ' . $sample->getValue();
+        return $sample->getName() . ' ' . $sample->getValue() . $timestampPart;
     }
 
     /**
diff --git a/src/Prometheus/Sample.php b/src/Prometheus/Sample.php
index efcba415..62e34606 100644
--- a/src/Prometheus/Sample.php
+++ b/src/Prometheus/Sample.php
@@ -26,6 +26,11 @@ class Sample
      */
     private $value;
 
+    /**
+     * @var int|null
+     */
+    private $timestamp;
+
     /**
      * Sample constructor.
      * @param mixed[] $data
@@ -36,6 +41,7 @@ public function __construct(array $data)
         $this->labelNames = (array) $data['labelNames'];
         $this->labelValues = (array) $data['labelValues'];
         $this->value = $data['value'];
+        $this->timestamp = $data['timestamp'];
     }
 
     /**
@@ -70,6 +76,11 @@ public function getValue(): string
         return (string) $this->value;
     }
 
+    public function getTimestamp(): ?int
+    {
+        return $this->timestamp;
+    }
+
     /**
      * @return bool
      */
diff --git a/src/Prometheus/Storage/InMemory.php b/src/Prometheus/Storage/InMemory.php
index 46445f8c..8b39a59b 100644
--- a/src/Prometheus/Storage/InMemory.php
+++ b/src/Prometheus/Storage/InMemory.php
@@ -96,6 +96,7 @@ private function collectHistograms(): array
                             'labelNames' => ['le'],
                             'labelValues' => array_merge($decodedLabelValues, [$bucket]),
                             'value' => $acc,
+                            'timestamp' => null,
                         ];
                     } else {
                         $acc += $histogramBuckets[$labelValues][$bucket];
@@ -104,6 +105,7 @@ private function collectHistograms(): array
                             'labelNames' => ['le'],
                             'labelValues' => array_merge($decodedLabelValues, [$bucket]),
                             'value' => $acc,
+                            'timestamp' => null,
                         ];
                     }
                 }
@@ -114,6 +116,7 @@ private function collectHistograms(): array
                     'labelNames' => [],
                     'labelValues' => $decodedLabelValues,
                     'value' => $acc,
+                    'timestamp' => null,
                 ];
 
                 // Add the sum
@@ -122,6 +125,7 @@ private function collectHistograms(): array
                     'labelNames' => [],
                     'labelValues' => $decodedLabelValues,
                     'value' => $histogramBuckets[$labelValues]['sum'],
+                    'timestamp' => null,
                 ];
             }
             $histograms[] = new MetricFamilySamples($data);
@@ -145,7 +149,7 @@ private function internalCollect(array $metrics): array
                 'labelNames' => $metaData['labelNames'],
                 'samples' => [],
             ];
-            foreach ($metric['samples'] as $key => $value) {
+            foreach ($metric['samples'] as $key => [$value, $timestamp]) {
                 $parts = explode(':', $key);
                 $labelValues = $parts[2];
                 $data['samples'][] = [
@@ -153,6 +157,7 @@ private function internalCollect(array $metrics): array
                     'labelNames' => [],
                     'labelValues' => $this->decodeLabelValues($labelValues),
                     'value' => $value,
+                    'timestamp' => $timestamp,
                 ];
             }
             $this->sortSamples($data['samples']);
@@ -212,12 +217,15 @@ public function updateGauge(array $data): void
             ];
         }
         if (array_key_exists($valueKey, $this->gauges[$metaKey]['samples']) === false) {
-            $this->gauges[$metaKey]['samples'][$valueKey] = 0;
+            $this->gauges[$metaKey]['samples'][$valueKey] = [0, $data['timestamp']];
         }
         if ($data['command'] === Adapter::COMMAND_SET) {
-            $this->gauges[$metaKey]['samples'][$valueKey] = $data['value'];
+            $this->gauges[$metaKey]['samples'][$valueKey] = [$data['value'], $data['timestamp']];
         } else {
-            $this->gauges[$metaKey]['samples'][$valueKey] += $data['value'];
+            $this->gauges[$metaKey]['samples'][$valueKey] = [
+                $this->gauges[$metaKey]['samples'][$valueKey][0] + $data['value'],
+                $data['timestamp']
+            ];
         }
     }
 
@@ -235,12 +243,15 @@ public function updateCounter(array $data): void
             ];
         }
         if (array_key_exists($valueKey, $this->counters[$metaKey]['samples']) === false) {
-            $this->counters[$metaKey]['samples'][$valueKey] = 0;
+            $this->counters[$metaKey]['samples'][$valueKey] = [0, $data['timestamp']];
         }
         if ($data['command'] === Adapter::COMMAND_SET) {
-            $this->counters[$metaKey]['samples'][$valueKey] = 0;
+            $this->counters[$metaKey]['samples'][$valueKey] = [0, $data['timestamp']];
         } else {
-            $this->counters[$metaKey]['samples'][$valueKey] += $data['value'];
+            $this->counters[$metaKey]['samples'][$valueKey] = [
+                $this->counters[$metaKey]['samples'][$valueKey][0] + $data['value'],
+                $data['timestamp']
+            ];
         }
     }
 
diff --git a/tests/Test/Prometheus/RenderTextFormatTest.php b/tests/Test/Prometheus/RenderTextFormatTest.php
index 5fa00048..f94561c9 100644
--- a/tests/Test/Prometheus/RenderTextFormatTest.php
+++ b/tests/Test/Prometheus/RenderTextFormatTest.php
@@ -34,9 +34,13 @@ private function buildSamples(): array
         $registry = new CollectorRegistry(new InMemory(), false);
         $registry->getOrRegisterCounter($namespace, 'counter', 'counter-help-text', ['label1', 'label2'])
                  ->inc(['bob', 'al\ice']);
-        $registry->getOrRegisterGauge($namespace, 'gauge', 'counter-help-text', ['label1', 'label2'])
+        $registry->getOrRegisterCounter($namespace, 'counter_with_timestamp', 'counter-with-timestamp-help-text', ['label1', 'label2'])
+                 ->inc(['bob', 'al\ice'], 1395066363000);
+        $registry->getOrRegisterGauge($namespace, 'gauge', 'gauge-help-text', ['label1', 'label2'])
                  ->inc(["bo\nb", 'ali\"ce']);
-        $registry->getOrRegisterHistogram($namespace, 'histogram', 'counter-help-text', ['label1', 'label2'], [0, 10, 100])
+        $registry->getOrRegisterGauge($namespace, 'gauge_with_timestamp', 'gauge-with-timestamp-help-text', ['label1', 'label2'])
+                 ->inc(["bo\nb", 'ali\"ce'], 1395066363000);
+        $registry->getOrRegisterHistogram($namespace, 'histogram', 'histogram-help-text', ['label1', 'label2'], [0, 10, 100])
                  ->observe(5, ['bob', 'alice']);
 
         return $registry->getMetricFamilySamples();
@@ -48,10 +52,16 @@ private function getExpectedOutput(): string
 # HELP mynamespace_counter counter-help-text
 # TYPE mynamespace_counter counter
 mynamespace_counter{label1="bob",label2="al\\\\ice"} 1
-# HELP mynamespace_gauge counter-help-text
+# HELP mynamespace_counter_with_timestamp counter-with-timestamp-help-text
+# TYPE mynamespace_counter_with_timestamp counter
+mynamespace_counter_with_timestamp{label1="bob",label2="al\\\\ice"} 1 1395066363000
+# HELP mynamespace_gauge gauge-help-text
 # TYPE mynamespace_gauge gauge
 mynamespace_gauge{label1="bo\\nb",label2="ali\\\\\"ce"} 1
-# HELP mynamespace_histogram counter-help-text
+# HELP mynamespace_gauge_with_timestamp gauge-with-timestamp-help-text
+# TYPE mynamespace_gauge_with_timestamp gauge
+mynamespace_gauge_with_timestamp{label1="bo\\nb",label2="ali\\\\\"ce"} 1 1395066363000
+# HELP mynamespace_histogram histogram-help-text
 # TYPE mynamespace_histogram histogram
 mynamespace_histogram_bucket{label1="bob",label2="alice",le="0"} 0
 mynamespace_histogram_bucket{label1="bob",label2="alice",le="10"} 1