iCloud: What is iCloud Calendar?
You can create and manage calendars for all areas of your life by using Calendar on iCloud.com. Changes you make appear automatically wherever you set up iCloud for Calendar. You never have to connect your device to your computer to keep your calendars current.
On iPhone, iPad, iPod touch, or Mac: Changes appear in your Calendar app.
On Windows: Changes appear in Microsoft Outlook.
Calendar alerts also appear in Notification Center on your iOS devices and Mac computers.
To use iCloud Calendar, go to icloud.com/calendar and sign in with your Apple ID (if you’re not signed in already).
If you don’t see Calendar on iCloud.com, your account just has access to iCloud web-only features. To gain access to iCloud Calendar and other iCloud features, set up iCloud on your iOS device or Mac.
If you’re already using another iCloud app, click the app’s name at the top of the iCloud.com window, then click Calendar.
When working with iCloud Calendar, make sure you use a browser recommended in the Apple Support article System requirements for iCloud.