Within 30 days iCloud data can be restored from iCloud online using PC or Mac.
- Go to https://www.icloud.com
- Select Settings
- Go to Restore Calendars and Reminders at the left bottom
- Select a backup to restore
- All sharing info will be removed. You will have to share these calendars and reminders again or ask their owners to share them
- All scheduled events will be cancelled and recreated, and invitations reissued. The scheduled invitees will first see a cancellation and then a new invitation
- The archive of calendars and reminders you have selected will replace calendars and reminders on all your devices. Your current calendars and reminders will be archived