timestamps are exported in local time instead of UTC

[olafhering]

Using %ci.%h for versionformat to have an ever increasing version number works only as long as everyone is in the same timezone.
There will be an apparent downgrade if one commits in timezone +0100 and the next commit is in timezone -0100, even if the commits are just seconds apart.

Please export the timestamps as UTC to avoid such backwards jumps.

Thank you.