Apple has added a new feature to iCloud that will allow you to restore deleted files, contacts and also calendars on iCloud.com.
When you visit the settings menu on iCloud.com there is now a new section which shows deleted files and also deleted contacts and calendars.
This could be a useful feature if you have accidentally deleted some files on iCloud.com, although restoring some items comes with some warnings, if you restore a deleted calendar, then it will resend invitations.
It appears that Apple now keeps these deleted files and data for around 30 days and their iCloud website shows how long there is left for each item before it is permanently deleted.
Source 9 to 5 Mac