What is iCloud Calendar?
You can create and manage calendars for all areas of your life by using Calendar on iCloud. Changes you make appear automatically on iCloud.com and wherever you set up iCloud for Calendar, including the Calendar app on your iPhone, iPad, iPod touch, or Mac; or Microsoft Outlook on a Windows computer.
Calendar alerts also appear in Notification Center on your iOS and iPadOS devices and Mac computers.
If you’re already using another iCloud feature, tap the feature’s name at the top of the iCloud.com window, then tap Calendar.
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 and iPadOS devices or Mac.