- +zone+: a timezone, which may be:
  - A string offset from UTC.
  - A single letter offset from UTC, in the range <tt>'A'..'Z'</tt>,
    <tt>'J'</tt> (the so-called military timezone) excluded.
  - An integer number of seconds.
  - A timezone object;
    see {Timezone Argument}[#class-Time-label-Timezone+Argument] for details.
- <tt>in: zone</tt>: a timezone _zone_, which may be as above.
