You should be able to accomplish this quite nicely with localtime and Time::Local.

As for whether the program has successfully run during the specified window, you'll need to implement some sort of queue to keep track of that. As jobs succeed, they should be removed from the queue... If they fail, they get pushed back onto the queue to be run with the other jobs for the next interval.

Update: BTW, what does Sat/36 actually mean? Is it this Saturday? or the next, etc? If you can change the spec, it's best to specify a date, as in 20070825/36 to eliminate any confusion.