We had a similar system at $job-2, we used
Date::Manip for it, specifically
Date::Manip::Recur. I hadn't touched the code that dealt with it, so I can't advice further.
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]