The notification will be sent 5 minutes before the program start.

If you have Android 13, make sure that the 'Notification' permission is enabled in the Android settings of the app.

For a notification to arrive on time on the latest versions of Android:
You have to go to the Android settings of the application and choose Battery then select: Unrestricted

If despite this, the notifications still arrive late, it is best to use:
The Share button then select your calendar.
You can choose the type of notification and be sure to get it on time.

Send me an email with your Android version if you have some difficulties.