If you accidentally deleted your calendars, bookmarks, or contacts from iCloud
You can go to iCloud.com to restore your missing calendars, bookmarks, or contacts from an earlier version.
When you restore from an earlier version, the version that you select will replace the existing calendars, bookmarks, or contacts on all your devices. Before you restore an earlier version, iCloud saves your current calendars, bookmarks, or contacts, so that if you want to undo the restore, you can. Just repeat the steps to restore, and select the latest date to restore from.
If you recently made changes, you might lose some data.
You might want to create a backup before restoring.
Restore your contacts or bookmarks from an earlier version
Sign in to iCloud.com.
Scroll down to the bottom of the window, then select Data Recovery.
Select Restore Contacts or Restore Bookmarks.
Select Restore next to the date before you deleted the content.
Select Restore again to confirm. After the restore completes, you get a notification on iCloud.com and an email at the address on file with your Apple ID.
Restore your calendars from an earlier version
Several things happen when you restore an earlier version of your calendars.
Your sharing settings get erased. You can share the calendars again, or you can ask the owner to share them again.
iCloud cancels and recreates all of your upcoming, scheduled events, then resends the invitations for you.
To restore your missing calendars:
Sign in to iCloud.com.
Scroll down to the bottom of the window, then select Data Recovery.
Select Restore Calendars.
Select Restore next to the date before you deleted the content.
Select Restore again to confirm. After the restore completes, you get a notification on iCloud.com and an email at the address on file with your Apple ID.
Undo a restore
To go back to the calendars, reminders, bookmarks, or contacts that you had before restoring:
Sign in to iCloud.com.
Scroll down to the bottom of the window, then select Data Recovery.
Select Restore Calendars, Restore Bookmarks, or Restore Contacts.
Select Restore next to the date that you restored.
Select Restore again to confirm. After the restore completes, you get a notification on iCloud.com and an email at the address on file with your Apple ID.