quakeforge/doc/timestamps.txt

To enable time-stamped messages in the server, set the Cvar sv_timestamps to a
value other than 0. When enabled, the string Cvar sv_timefmt is used to format
the date and time.

The following special codes are interpreted inside sv_timefmt strings.

       %a     The abbreviated weekday name according to the  cur<75>
              rent locale.

       %A     The  full  weekday  name  according  to the current
              locale.

       %b     The abbreviated month name according to the current
              locale.

       %B     The  full  month  name  according  to  the  current
              locale.

       %c     The preferred date and time representation for  the
              current locale.

       %d     The  day of the month as a decimal number (range 01
              to 31).

       %h     Equivalent to %b. (SU)

       %H     The  hour as a decimal number using a 24-hour clock
              (range 00 to 23).

       %I     The hour as a decimal number using a 12-hour  clock
              (range 01 to 12).

       %j     The  day of the year as a decimal number (range 001
              to 366).

       %k     The hour (24-hour clock) as a decimal number (range
              0  to  23);  single digits are preceded by a blank.
              (See also %H.) (TZ)

       %m     The month as a decimal number (range 01 to 12).

       %M     The minute as a decimal number (range 00 to 59).

       %p     Either `AM' or `PM' according  to  the  given  time
              value, or the corresponding strings for the current
              locale.  Noon is treated as `pm'  and  midnight  as
              `am'.

       %S     The second as a decimal number (range 00 to 61).

       %U     The week number of the current year  as  a  decimal
              number,  range  00  to  53, starting with the first
              Sunday as the first day of week 01. See also %V and
              %W.

       %w     The  day  of  the  week as a decimal, range 0 to 6,
              Sunday being 0.  See also %u.

       %W     The week number of the current year  as  a  decimal
              number,  range  00  to  53, starting with the first
              Monday as the first day of week 01.

       %x     The preferred date representation for  the  current
              locale without the time.

       %X     The  preferred  time representation for the current
              locale without the date.

       %y     The year as a  decimal  number  without  a  century
              (range 00 to 99).

       %Y     The year as a decimal number including the century.

       %Z     The time zone name or abbreviation.
       
       %%     A literal `%' character.