iCloud: Change a calendar’s time zone in iCloud
By default, your calendars and their events use the time zone set in Settings on iCloud.com. You can create events and view calendars in other time zones by turning on time zone support in Calendar on iCloud.com. This is useful, for example, if you’re traveling and want to schedule events according to the time zones in which they occur.
If you change your iCloud.com time zone while time zone support is on, the times of your calendar’s events change to the new time zone. If time zone support is off, the times continue to appear in their original time zone.
Note: Changes you make to the time zone appear on every device that has iCloud Calendar and time zone support turned on. Time zone support must be turned on individually for each device.
Click the Action pop-up menu in the sidebar, then choose Preferences.
Click Advanced, select “Enable time zone support,” then click Save.
With time zone support on, a Time Zone pop-up menu appears when you create an event, letting you set any time zone you want.