If the ``-s'' flag is used, then each argument is taken as a date string to be parsed by parsedate(3) and is output as a string formatted by ctime(3). This is the default.
If the ``-n'' flag is used, then each argument is converted the same way but is output as a time_t; see time(2).
If the ``-c'' flag is used, then each argument is taken to be a time_t and is output in ctime format.
For example,
% convdate 'feb 10 10am' Sun Feb 10 10:00:00 1991 % convdate 12pm 5/4/90 Fri Dec 13 00:00:00 1991 Fri May 4 00:00:00 1990 % convdate -n 'feb 10 10am' '12pm 5/4/90' 666198000 641880000 % convdate -c 666198000 Sun Feb 10 10:00:00 1991