Delete standard event

I have a green tag which specifies Mothers Day and similar standard events.

I cannot delete this.
Is there a way to delete there preset events?

Typically holiday calendars are read-only so you will not be able to delete a single event. You will need to remove the whole holiday calendar if you do not want to see its events.

If the holiday calendar was added from eM Client, you can delete it by right-click on the calendar folder under Holidays in the calendar section of eM Client.

If it comes from your calendar provider, you will be able to disable it in ther web interface.