I would suggest you take the time to study Time::Piece and/or DateTime instead of the basic localtime stuff you're doing here

Completely agree. I'd also point out that of the two Time::Piece is always my first port of call as it is small and in core and is good enough for 95% of the date/time work I need to do. By contrast, DateTime is a bit of a monster but it does cater pretty well for the remaining 5% of cases.