Advertisements in my calendar

Hi and welcome to the Apple (user-to-user) Community.

Re: "Advertisements in my calendar :

Everyday has an advertisement and I want to block access to my calendar to others"

If you are using iCloud to share calendars with others:

Share iCloud calendars on iPhone - Apple Support

says:

"Change a person’s access to a shared calendar

After you invite a person to share your calendar, you can turn on or off their ability to edit the calendar, or stop sharing the calendar with that person.

1. Tap Calendars, tap  next to the shared calendar, then tap the person’s name.
2. Do any of the following:

• • Turn Allow Editing on or off.
  • Tap Stop Sharing."

There is more info: in the above linked article:

Eg: If you wish, you can share a read-only version that anyone can view but not change.

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If you are not using iCloud:

You can unsubscribe from a calendar, if you want to:

You can unsubscribe from a calendar you’re subscribed to.

When you unsubscribe, you can also report the calendar as junk.

1. Tap Calendars at the bottom of the screen.
2. Tap  next to the calendar you want to unsubscribe from.
3. Tap Unsubscribe, then Tap Unsubscribe or Unsubscribe and Report Junk.
4. Note: When you tap Unsubscribe and Report Junk, the calendar is reported to Apple as a suspected junk subscription.

More info: Set up multiple calendars on iPhone - Apple Support

All the best :-)