iCloud

Create a calendar on iCloud.com
You can create and manage one or more calendars and access them on any iOS device, iPadOS device, or computer that has iCloud Calendar turned on.

In Calendar on iCloud.com, click the Action pop-up menu
in the bottom-left corner, then choose New Calendar.
Type a name for the calendar, then press Return.
Your calendars are listed in the sidebar on the left.
You can view as many calendars as you want at the same time.
iCloud Calendar comes with two already-created calendars: Home and Work. You can rename or delete them, but you must always have at least one calendar in the list.