diff --git a/composer.json b/composer.json
index f2f8b90..607dec3 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
         "jimdo/prometheus_client_php": "*"
     },
     "require": {
-        "php": "^7.2",
+        "php": "^7.2|^8.0",
         "ext-json": "*",
         "guzzlehttp/guzzle": "^6.3",
         "symfony/polyfill-apcu": "^1.6"
diff --git a/src/Prometheus/Counter.php b/src/Prometheus/Counter.php
index 1b095e5..0c8faef 100644
--- a/src/Prometheus/Counter.php
+++ b/src/Prometheus/Counter.php
@@ -29,8 +29,9 @@ public function inc(array $labels = []): void
     /**
      * @param int $count e.g. 2
      * @param array $labels e.g. ['status', 'opcode']
+     * @param int|null $timestamp
      */
-    public function incBy($count, array $labels = []): void
+    public function incBy($count, array $labels = [], int $timestamp = null): void
     {
         $this->assertLabelsAreDefinedCorrectly($labels);
 
@@ -43,6 +44,7 @@ public function incBy($count, array $labels = []): void
                 'labelValues' => $labels,
                 'value' => $count,
                 'command' => Adapter::COMMAND_INCREMENT_INTEGER,
+                'timestamp' => $timestamp
             ]
         );
     }
diff --git a/src/Prometheus/Gauge.php b/src/Prometheus/Gauge.php
index 72189f7..c2937b2 100644
--- a/src/Prometheus/Gauge.php
+++ b/src/Prometheus/Gauge.php
@@ -13,8 +13,9 @@ class Gauge extends Collector
     /**
      * @param double $value e.g. 123
      * @param array $labels e.g. ['status', 'opcode']
+     * @param int|null $timestamp
      */
-    public function set(float $value, array $labels = []): void
+    public function set(float $value, array $labels = [], int $timestamp = null): void
     {
         $this->assertLabelsAreDefinedCorrectly($labels);
 
@@ -27,6 +28,7 @@ public function set(float $value, array $labels = []): void
                 'labelValues' => $labels,
                 'value' => $value,
                 'command' => Adapter::COMMAND_SET,
+                'timestamp' => $timestamp
             ]
         );
     }
@@ -50,8 +52,9 @@ public function inc($labels = []): void
     /**
      * @param $value
      * @param array $labels
+     * @param int|null $timestamp
      */
-    public function incBy($value, array $labels = []): void
+    public function incBy($value, array $labels = [], int $timestamp = null): void
     {
         $this->assertLabelsAreDefinedCorrectly($labels);
 
@@ -64,6 +67,7 @@ public function incBy($value, array $labels = []): void
                 'labelValues' => $labels,
                 'value' => $value,
                 'command' => Adapter::COMMAND_INCREMENT_FLOAT,
+                'timestamp' => $timestamp
             ]
         );
     }
diff --git a/src/Prometheus/RenderTextFormat.php b/src/Prometheus/RenderTextFormat.php
index a5b78dc..49907b4 100644
--- a/src/Prometheus/RenderTextFormat.php
+++ b/src/Prometheus/RenderTextFormat.php
@@ -37,6 +37,7 @@ public function render(array $metrics): string
      */
     private function renderSample(MetricFamilySamples $metric, Sample $sample): string
     {
+        $result = null;
         $escapedLabels = [];
 
         $labelNames = $metric->getLabelNames();
@@ -45,9 +46,14 @@ private function renderSample(MetricFamilySamples $metric, Sample $sample): stri
             foreach ($labels as $labelName => $labelValue) {
                 $escapedLabels[] = $labelName . '="' . $this->escapeLabelValue($labelValue) . '"';
             }
-            return $sample->getName() . '{' . implode(',', $escapedLabels) . '} ' . $sample->getValue();
+            $result = $sample->getName() . '{' . implode(',', $escapedLabels) . '} ' . $sample->getValue();
+        } else {
+            $result = $sample->getName() . ' ' . $sample->getValue();
         }
-        return $sample->getName() . ' ' . $sample->getValue();
+        if ($sample->hasTimestamp()) {
+            $result .= ' ' . $sample->getTimestamp() * 1000;
+        }
+        return $result;
     }
 
     /**
@@ -56,6 +62,7 @@ private function renderSample(MetricFamilySamples $metric, Sample $sample): stri
      */
     private function escapeLabelValue($v): string
     {
+        $v = is_array($v) ? $v : strval($v);
         $v = str_replace("\\", "\\\\", $v);
         $v = str_replace("\n", "\\n", $v);
         $v = str_replace("\"", "\\\"", $v);
diff --git a/src/Prometheus/Sample.php b/src/Prometheus/Sample.php
index c8774e8..1aec8bc 100644
--- a/src/Prometheus/Sample.php
+++ b/src/Prometheus/Sample.php
@@ -26,6 +26,11 @@ class Sample
      */
     private $value;
 
+    /**
+     * @var ?int
+     */
+    private $timestamp;
+
     /**
      * Sample constructor.
      * @param array $data
@@ -36,6 +41,7 @@ public function __construct(array $data)
         $this->labelNames = $data['labelNames'];
         $this->labelValues = $data['labelValues'];
         $this->value = $data['value'];
+        $this->timestamp = (int)($data['timestamp'] ?? 0) ?: null;
     }
 
     /**
@@ -67,7 +73,7 @@ public function getLabelValues(): array
      */
     public function getValue(): string
     {
-        return (string) $this->value;
+        return (string)$this->value;
     }
 
     /**
@@ -77,4 +83,20 @@ public function hasLabelNames(): bool
     {
         return !empty($this->labelNames);
     }
+
+    /**
+     * @return int|null
+     */
+    public function getTimestamp(): ?int
+    {
+        return $this->timestamp;
+    }
+
+    /**
+     * @return bool
+     */
+    public function hasTimestamp(): bool
+    {
+        return (bool)$this->timestamp;
+    }
 }
diff --git a/src/Prometheus/Storage/InMemory.php b/src/Prometheus/Storage/InMemory.php
index bfd4c70..de0a38f 100644
--- a/src/Prometheus/Storage/InMemory.php
+++ b/src/Prometheus/Storage/InMemory.php
@@ -125,11 +125,13 @@ private function internalCollect(array $metrics): array
             foreach ($metric['samples'] as $key => $value) {
                 $parts = explode(':', $key);
                 $labelValues = $parts[2];
+                $timestamp = $parts[3] ?? false;
                 $data['samples'][] = [
                     'name' => $metaData['name'],
                     'labelNames' => [],
                     'labelValues' => $this->decodeLabelValues($labelValues),
                     'value' => $value,
+                    'timestamp' => $timestamp
                 ];
             }
             $this->sortSamples($data['samples']);
@@ -261,6 +263,7 @@ private function valueKey(array $data): string
             $data['type'],
             $data['name'],
             $this->encodeLabelValues($data['labelValues']),
+            $data['timestamp'] ?? false,
             'value'
         ]);
     }