In order to delete a subscribed calendar, you will need to unsubscribe from the calendar.
1) Click on “Settings” in the upper right-hand corner of your Google Calendar page.
2) Click on “Calendar Settings”.
3) Scroll down until you see “Subscribed calendars”.
4) Click the three dots next to the calendar name and click “Unsubscribe”.
iOS 15: How to Delete Subscribed Virus Calendar on iPhone (iOS 14/iOS 15) or iPad in 
You can delete calendars on iPhone by following these steps:
Open the Settings app, scroll down to “Mail, Contacts, Calendars,” and tap on “Subscribed Calendars.” Tap the calendar you want to delete and then tap “Delete Subscription.
You can unsubscribe from a calendar by going to Settings > Mail, Contacts, Calendars > Subscribed Calendars. From there you can tap on the calendar that you want to unsubscribe from and then tap “Unsubscribe”.
The calendar app on the iPhone allows you to subscribe to different calendars. This is helpful if you have a calendar that is not synced with your phone but want to stay up-to-date on it.
There are two ways to delete a subscribed calendar iOS 15. The first way is to go to the Settings app and select “Mail, Contacts, Calendars” and then select the calendar you want to delete. Once on the calendar’s detail page, tap on “Unsubscribe”. This will remove the subscription from your phone. The second way is to open the Calendar app, tap on “Calendars”, and then hit “Edit”.