iCloud: Change your calendar’s time zone
If time zone support is on, your calendar doesn’t update if you move between time zones. For example, if you have a meeting at 10 a.m. Pacific time in California, and you fly to New York, that meeting still appears at 10 a.m. in iCloud Calendar.
If time zone support is off, your calendar moves as you move; that is, the time zone settings update as you change time zones. For example, if you have a meeting at 10 a.m. Pacific time in California and fly to New York, your calendar items are shown in local (eastern) time. So your meeting at 10 a.m. Pacific time shows up at 1 p.m. eastern time.
Use a time zone other than the default
In iCloud Calendar, choose Preferences from the Action pop-up menu below the sidebar.
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.
You can also reset the default time zone for your calendars (and their events) at any time.