diff --git a/CHANGELOG.md b/CHANGELOG.md
index 07442d3..644249a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.11.0
+
+- Added `Clock` implementation with `SystemClock` and `FixedClock`.
+
 ## 0.10.0
 
 - Added `is*InTimeZone(Time | Date | Month | Year $equalTo, \DateTimeZone $timeZone): bool` methods to `Moment`.
diff --git a/UPGRADE.md b/UPGRADE.md
index d737226..39e9d4d 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -1,5 +1,9 @@
 # Upgrade guide
 
+## From 0.10.* to 0.11.0
+
+No breaking changes.
+
 ## From 0.9.* to 0.10.0
 
 No breaking changes (just deprecations).
@@ -38,11 +42,11 @@ When using `MomentType`, you need to migrate the database column to support mill
 
 ## From 0.6.* to 0.7.0
 
-No breaking changes
+No breaking changes.
 
 ## From 0.5.* to 0.6.0
 
-No breaking changes
+No breaking changes.
 
 ## From 0.4.* to 0.5.0
 
@@ -50,7 +54,7 @@ You can remove `YearNormalizer` from your normalizers if you registered it manua
 
 ## From 0.3.* to 0.4.0
 
-No breaking changes
+No breaking changes.
 
 ## From 0.2.* to 0.3.0
 
@@ -85,4 +89,4 @@ if ($date->day === 15) {
 
 ## From 0.1.* to 0.2.0
 
-No breaking changes
+No breaking changes.
diff --git a/docker-compose.yml b/docker-compose.yml
index 1296c87..215afe8 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,5 +1,3 @@
-version: '3.7'
-
 services:
 
   php-8.2:
diff --git a/src/Clock/Clock.php b/src/Clock/Clock.php
new file mode 100644
index 0000000..9d2bfd3
--- /dev/null
+++ b/src/Clock/Clock.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DigitalCraftsman\DateTimePrecision\Clock;
+
+use DigitalCraftsman\DateTimePrecision\Moment;
+
+interface Clock
+{
+    public function now(): Moment;
+}
diff --git a/src/Clock/FrozenClock.php b/src/Clock/FrozenClock.php
new file mode 100644
index 0000000..fabaed8
--- /dev/null
+++ b/src/Clock/FrozenClock.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DigitalCraftsman\DateTimePrecision\Clock;
+
+use DigitalCraftsman\DateTimePrecision\Moment;
+
+final class FrozenClock implements Clock
+{
+    private Moment $moment;
+
+    public function __construct(?Moment $moment = null)
+    {
+        $this->moment = $moment ?? Moment::fromDateTime(new \DateTimeImmutable('now'));
+    }
+
+    public function freeze(Moment $moment): void
+    {
+        $this->moment = $moment;
+    }
+
+    #[\Override]
+    public function now(): Moment
+    {
+        return $this->moment;
+    }
+}
diff --git a/src/Clock/SystemClock.php b/src/Clock/SystemClock.php
new file mode 100644
index 0000000..4c23117
--- /dev/null
+++ b/src/Clock/SystemClock.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DigitalCraftsman\DateTimePrecision\Clock;
+
+use DigitalCraftsman\DateTimePrecision\Moment;
+
+final readonly class SystemClock implements Clock
+{
+    #[\Override]
+    public function now(): Moment
+    {
+        return Moment::fromDateTime(new \DateTimeImmutable(
+            'now',
+            new \DateTimeZone('UTC'),
+        ));
+    }
+}
diff --git a/tests/Clock/FrozenClockTest.php b/tests/Clock/FrozenClockTest.php
new file mode 100644
index 0000000..14bbf81
--- /dev/null
+++ b/tests/Clock/FrozenClockTest.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DigitalCraftsman\DateTimePrecision\Clock;
+
+use DigitalCraftsman\DateTimePrecision\Moment;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(FrozenClock::class)]
+final class FrozenClockTest extends TestCase
+{
+    #[Test]
+    public function construction_works(): void
+    {
+        // -- Arrange
+        $moment = Moment::fromStringInTimeZone('2024-05-06 08:00:00', new \DateTimeZone('Europe/Berlin'));
+
+        // -- Act
+        $clock = new FrozenClock($moment);
+
+        // -- Assert
+        self::assertSame($moment, $clock->now());
+    }
+
+    #[Test]
+    public function freeze_works(): void
+    {
+        // -- Arrange
+        $clock = new FrozenClock();
+        $moment = Moment::fromStringInTimeZone('2024-05-06 08:00:00', new \DateTimeZone('Europe/Berlin'));
+
+        // -- Act
+        $clock->freeze($moment);
+
+        // -- Assert
+        self::assertSame($moment, $clock->now());
+    }
+}
diff --git a/tests/Clock/SystemClockTest.php b/tests/Clock/SystemClockTest.php
new file mode 100644
index 0000000..e78f271
--- /dev/null
+++ b/tests/Clock/SystemClockTest.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DigitalCraftsman\DateTimePrecision\Clock;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Only very little that's possible to test here, so we do what's possible.
+ */
+#[CoversClass(SystemClock::class)]
+final class SystemClockTest extends TestCase
+{
+    #[Test]
+    public function now_works(): void
+    {
+        // -- Arrange
+        $clock = new SystemClock();
+
+        // -- Act
+        $moment = $clock->now();
+
+        // -- Assert
+        self::assertEquals($moment->dateTime->getTimezone(), new \DateTimeZone('UTC'));
+    }
+}