My iCloud account doesn't have a calendar?
If you haven't signed in with your Apple ID on an Apple device at least once in its history, these are the only services available to you.


  What is web-only access to iCloud?
  
  Web-only access is a free level of iCloud service that's available to anyone, including people who don't own or use Apple devices. It includes access to Pages, Numbers, and Keynote for iCloud and 1 GB of free storage for any documents you create.


You can obtain the other features by signing in on an Apple device.


  How do I get the full set of iCloud features?
  
  If you have an iOS device or Mac, you can get the full set of iCloud features. Simply sign in to iCloud in Settings on your iOS device or System Preferences on your Mac. You'll get immediate access to all iCloud features and 5 GB of free storage. You can also choose additional storage plans from your device.


For more information, see this Apple KB article:


Web-only access to iCloud