diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1ac4a6f..82f52b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,3 +3,4 @@
 * Set default version to "git-main" to indicate development environment
 * Add homepage, link to it from the logo
 * Make it possible to add a new platform
+* Save calculated duration to database if both timestamps are set
diff --git a/src/web/tracker/models.py b/src/web/tracker/models.py
index 06da9b9..50db664 100644
--- a/src/web/tracker/models.py
+++ b/src/web/tracker/models.py
@@ -52,3 +52,8 @@ class Session(models.Model):
             if self.duration_manual == None
             else self.duration_manual + self.calculated_duration()
         )
+
+    def save(self, *args, **kwargs):
+        if self.timestamp_start != None and self.timestamp_end != None:
+            self.duration_calculated = self.timestamp_end - self.timestamp_start
+        super(Session, self).save(*args, **kwargs)