Modernize function implementations and docstrings in scripts/time. * addtodate.m: Add millisecond functionality. Update docstring and %!tests. * calendar.m: Implement faster way to add '*' to day display. Update docstring. * weekday.m: Use more modern coding stytle. Update docstring. * asctime.m, clock.m, ctime.m, date.m, datenum.m, datestr.m, datevec.m, eomday.m, etime.m, is_leap_year.m: Update docstring and/or use Octave formatting spacing conventions for %!tests.