macOS Calendar adds “1 day before” alert to all-day events despite all default alerts set to “None”

Hello,

I am experiencing a persistent issue with the Calendar app on macOS.

When I create a new all-day event on my Mac, the Calendar app automatically adds an alert “1 day before”, even though:

• Default alerts for all-day events are set to “None” in Calendar settings
• Default alerts are also set to “None” on my iPhone
• Default alerts are also set to “None” in iCloud Calendar settings in a web browser

This does not happen when creating the same all-day event on iPhone. The issue happens only for events created on my mac.

Changing the default alert (for example to “1 week before”) and restarting the Calendar app does not help, new all-day events still get an automatic “1 day before” alert.

Could you please help if there is a fix for this?

Thank you.