in reply to Subtract Hours

Assuming both times are in the same timezone and no change in DST between the two the anser is correct "+ k times 24 hours, for every integer value of k".

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

In Section Seekers of Perl Wisdom