Time zone invariant alarms

Allow creating alarms with a time zone (for example, the user’s home time zone - similar to how Google Calendar allows events to have time zones). With a timezone, the alarm goes off the same “time” regardless the local time the user has travelled to.

This feature would be especially useful for people who do something every 24 hours, like take a medication, and may not otherwise remember to update their alarm to the correct local time.