fmtclock clockval ?format? ?GMT|{}?
              Converts  a  Unix  integer  time  value,  typically
              returned by getclock, convertclock, or  the  atime,
              mtime,  or  ctime  options  of the file command, to
              human-readable form.   The  format  argument  is  a
              string  that describes how the date and time are to
              be formatted.  Field descriptors consist of a ``%''
              followed  by  a  field  descriptor  character.  All
              other characters are copied into the result.  Valid
              field descriptors are:

                  %% - Insert a %.
                  %a - Abbreviated weekday name.
                  %A - Full weekday name
                  %b - Abbreviated month name.
                  %B - Full month name.
                  %d - Day of month (01 - 31).
                  %D - Date as %m/%d/%y.
                  %e - Day of month (1-31), no leading zeros.
                  %h - Abbreviated month name.
                  %H - Hour (00 - 23).
                  %I - Hour (00 - 12).
                  %j - Day number of year (001 - 366).
                  %m - Month number (01 - 12).
                  %M - Minute (00 - 59).
                  %n - Insert a new line.
                  %p - AM or PM.
                  %r - Time as %I:%M:%S %p.
                  %R - Time as %H:%M.
                  %S - Seconds (00 - 59).
                  %t - Insert a tab.
                  %T - Time as %H:%M:%S.
                  %U - Week number of year (01 - 52), Sunday is the first
                       day of the week.
                  %w - Weekday number (Sunday = 0).
                  %W - Week number of year (01 - 52), Monday is the first
                       day of the week.
                  %x - Local specific date format.
                  %X - Local specific time format.
                  %y - Year within century (00 - 99).
                  %Y - Year as ccyy (e.g. 1990)
                  %Z - Time zone name.

              If  format  is not specified, "%a %b %d %H:%M:%S %Z
              %Y" is used.  If GMT is specified, the time will be
              formated as Greenwich Mean Time. If the argument is
              not specified or is empty, then the local  timezone
              will be used as defined by the TIMEZONE environment
              variable.

              This command is provided by Extended Tcl.