rcs: Date option

 
 2.1.2 Date option
 -----------------
 
 Some commands accept an option of the form ‘-dDATE’ to specify a “date”,
 an absolute point in time (to second resolution), expressed in a “date
 format”.  These also accept ‘-zZONE’ to specify the timezone.  The
 special value ‘LT’ stands for the “local time zone”.  RCS recognizes
 many date formats and time zones.  For example, the following dates are
 equivalent if local time is January 11, 1990, 8pm Pacific Standard Time,
 eight hours west of Coordinated Universal Time (UTC):
 
      8:00 pm lt
      4:00 AM, Jan. 12, 1990           default is UTC
      1990-01-12 04:00:00+00           ISO 8601 (UTC)
      1990-01-11 20:00:00-08           ISO 8601 (local time)
      1990/01/12 04:00:00              traditional RCS format
      Thu Jan 11 20:00:00 1990 LT      output of ctime(3) + LT
      Thu Jan 11 20:00:00 PST 1990     output of date(1)
      Fri Jan 12 04:00:00 GMT 1990
      Thu, 11 Jan 1990 20:00:00 -0800  Internet RFC 822
      12-January-1990, 04:00 WET
 
 Most fields in the date and time can be defaulted.  The default time
 zone is normally UTC, but this can be overridden by the ‘-z’ option.
 The other defaults are determined in the order year, month, day, hour,
 minute, and second (most to least significant).  At least one of these
 fields must be provided.  For omitted fields that are of higher
 significance than the highest provided field, the time zone’s current
 values are assumed.  For all other omitted fields, the lowest possible
 values are assumed.  For example, without ‘-z’, the date ‘20, 10:30’
 defaults to ‘10:30:00 UTC’ of the 20th of the UTC time zone’s current
 month and year.  Note that for the shell, the date/time must be quoted
 if it contains spaces.
 
    RCS also accepts some other formats which specify only the date
 portion (omitting the time portion).  In the following table, YEAR is
 the four-digit year ‘YYYY’, and all examples specify 20 April 2018.
 
 format           example          description
                                   
 ---------------------------------------------------------------------------
 YEAR-DOY         ‘2018-110’       DOY is the day of year ‘DDD’, 1-366.
                                   
 YEAR-wWEEK-DOW   ‘2018-w16-5’     WEEK is the ISO week number ‘WW’, 0-53
                                   (actually, ISO week numbers are 1-53;
                                   week 0 is a GNU RCS extension); and
                                   DOW is the ISO day number ‘D’, 1-7
                                   (Monday through Sunday).  Note the
                                   literal ‘w’ that precedes WEEK.