Timezone handling

[dylmye]

Current issues:

• In tz behind UTC, starts at date on trip details shows the day before
• In tz behind UTC, item ends at validation is off by tz offset meaning if you are in -4 then any events past 20:00 are invalid
• Creating a trip item makes the starts at/ends at on said item off, editing it works correctly behind UTC but ahead of UTC you have to subtract the offset when you set it to a different day (so to make an event at 6pm in +1 you have to set it at 5pm)
• The countdown on trip list doesnt account for timezone
• In tz ahead of UTC, starts at + ends at dates on trip details shows the day before, editing it works correctly