I have a vivo activ 3 calendar shows holidays that have no relevance? Where do these come from?
Check again online in the settings so you haven't hidden any calendars from the list: https://calendar.google.com/calendar/u/0/r/settings
Hidden calendars got an overcrossed eye. I'm not sure how that affects the calendar provider that Garmin use, but better to check.
Do you see your other scheduled events in the calendar?