diff --git a/CHANGELOG.md b/CHANGELOG.md
index 310c0e2..6ec9b0e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+2.3.3 (unreleased)
+=====
+
+* (improvement) Simplify task run duration calculation.
+
+
+
 2.3.2
 =====
 
diff --git a/src/Duration/DurationCalculator.php b/src/Duration/DurationCalculator.php
new file mode 100644
index 0000000..92d3494
--- /dev/null
+++ b/src/Duration/DurationCalculator.php
@@ -0,0 +1,25 @@
+<?php declare(strict_types=1);
+
+namespace Torr\TaskManager\Duration;
+
+/**
+ * @final
+ */
+readonly class DurationCalculator
+{
+	/**
+	 * Returns the duration in nanoseconds
+	 */
+	public function calculateDuration (\DateTimeImmutable $start, \DateTimeImmutable $end) : float
+	{
+		$diff = $start->diff($end, true);
+
+		$seconds = $diff->days * 24 * 60 * 60
+			+ $diff->h * 60 * 60
+			+ $diff->i * 60
+			+ $diff->s
+			+ $diff->f;
+
+		return $seconds / 1e9;
+	}
+}
diff --git a/src/Entity/TaskRun.php b/src/Entity/TaskRun.php
index 3e96751..fefc519 100644
--- a/src/Entity/TaskRun.php
+++ b/src/Entity/TaskRun.php
@@ -4,6 +4,7 @@
 
 use Doctrine\DBAL\Types\Types;
 use Doctrine\ORM\Mapping as ORM;
+use Torr\TaskManager\Duration\DurationCalculator;
 use Torr\TaskManager\Exception\Log\InvalidLogActionException;
 
 use function Symfony\Component\Clock\now;
@@ -55,11 +56,6 @@ class TaskRun
 	 */
 	#[ORM\Column(type: Types::TEXT, nullable: true)]
 	private ?string $output = null;
-
-	/**
-	 *
-	 */
-	private ?float $start = null;
 	// endregion
 
 	/**
@@ -68,7 +64,6 @@ public function __construct (TaskLog $taskLog)
 	{
 		$this->taskLog = $taskLog;
 		$this->timeStarted = now();
-		$this->start = hrtime(true);
 	}
 
 	// region Accessors
@@ -164,14 +159,9 @@ private function finalizeRun (
 			throw new InvalidLogActionException("Can't finalize task run #{$this->id} as it is already finished.");
 		}
 
-		if (null === $this->start)
-		{
-			throw new InvalidLogActionException("Can't finalize a task that wasn't started in this run.");
-		}
-
 		$this->success = $success;
 		$this->finishedProperly = $finishedProperly;
 		$this->output = $output;
-		$this->duration = hrtime(true) - $this->start;
+		$this->duration = new DurationCalculator()->calculateDuration($this->timeStarted, now());
 	}
 }
diff --git a/tests/Duration/DurationCalculatorTest.php b/tests/Duration/DurationCalculatorTest.php
new file mode 100644
index 0000000..eb63f6c
--- /dev/null
+++ b/tests/Duration/DurationCalculatorTest.php
@@ -0,0 +1,60 @@
+<?php declare(strict_types=1);
+
+namespace Tests\Torr\TaskManager\Duration;
+
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use Torr\TaskManager\Duration\DurationCalculator;
+
+/**
+ * @internal
+ */
+final class DurationCalculatorTest extends TestCase
+{
+	/**
+	 *
+	 */
+	public static function provideCalculation () : iterable
+	{
+		yield "hours-minutes-seconds-microseconds" => [
+			"2020-01-01 00:00:00.000000",
+			"2020-01-01 01:02:03.123456",
+			(3600 + 120 + 3.123456) / 1e9,
+		];
+
+		yield "years" => [
+			"2021-01-01 00:00:00.000000",
+			"2022-01-01 00:00:00.000000",
+			(365 * 24 * 60 * 60) / 1e9,
+		];
+
+		yield "months" => [
+			"2021-01-01 00:00:00.000000",
+			"2021-02-01 00:00:00.000000",
+			(31 * 24 * 60 * 60) / 1e9,
+		];
+
+		yield "days" => [
+			"2021-01-01 00:00:00.000000",
+			"2021-01-04 00:00:00.000000",
+			(3 * 24 * 60 * 60) / 1e9,
+		];
+	}
+
+	/**
+	 *
+	 */
+	#[DataProvider("provideCalculation")]
+	public function testCalculation (
+		string $start,
+		string $end,
+		float $expected,
+	) : void
+	{
+		$start = \DateTimeImmutable::createFromFormat("!Y-m-d H:i:s.u", $start);
+		$end = \DateTimeImmutable::createFromFormat("!Y-m-d H:i:s.u", $end);
+		$calculator = new DurationCalculator();
+
+		self::assertSame($expected, $calculator->calculateDuration($start, $end));
+	}
+}