The fourth parameter to Koha::DateUtils::output_pref is $dateonly, which allows the user to specify that the time should not be included in the returned date string. Now that there is a $force_time format (which perhaps might be better called $date_format), it would probably be better to eliminate $dateonly, and use a time format of "none" when the time is not wanted.
Martin or Joubu, could you assist me in my quest to clean up the 4 digit bugs and let me know if this is still desirable? :)
Could be, but that's not going to bring us many benefits. And I actually think I prefer to have it separate, especially because timeformat is also a syspref.