How do I enable popups in Google Calendar when tab is closed?
If you're using Google Chrome, you can add the Chrome App.
You can try using a Calendar lab called "Gentle reminders"
Go to your calendar settings and click the
Labs tab at the top. Look for Gentle Reminders and click
Enable then remember to save your changes.
Go back into your settings and you should now see (in the
General tab) the options for Gentle Reminders. Try using desktop notifications - it will pop up a desktop notification near the system tray when an event is coming up.