Expl: in `git log --after=2008-10-01` the time defaults to the time the command is run.
So e.g. the command is equiv to `git log --after="2008-10-01 09:00:00"` when run at 09:00:00
how to robustly use `git log` and limit the commits by date/time

* show that CommitDate is considered, when using `--after` and `--before`
* show that `--after` means on-or-after and `--before` means on-or-before
* best practices: show how to limit by absolute time (ISO format),
  so that the log command's results are identical for everyone around the
  world
* format dates returned by git log according to your timezone of choice,
  using TZ (tested on GNU/Linux and Windows) and `--date=local`
* explain how `--after=2008-06-01` default to using time when command is
  run; and how offsets from UTC are (in this case) not corrected for
  DST changes.
minor: fix code formatting (for pdf output)
provide timezone-examples from different Cities
* Auckland/New Zealand, Berlin, etc. -- not just Paris
* minor corrections
minor: remove repetition ("committed")
shorten explanation for `git log --after=2008-06-01` (date-only)
`git log --after=2008-06-01` keeps timezone offset from UTC equiv.
to the time when it is run on your computer.
Saying this is "disregarding Daylight Saving Time" is confusing,
because it could lead one to mistakenly assume that git then
only considers summer-time, or only winter-time. But this is
not the case. Git just keeps the offset from UTC identical.
Merge pull request #750 from nicesw123/timeissue

Explain: `git log --after=2008-10-01` has differing results, depending on time the command is run