A future change will include an NSTimeZone hook so we can determine
the device's current time zone.

Change-Id: Ia4bd6b955e4cb720c518055541b66ff57a4dd303
Reviewed-on: https://go-review.googlesource.com/6511Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: David Crawshaw <crawshaw@golang.org>