Have a nice month!

"have a nice day"

"you have an even nicer one"

This one is my favorite

I often just wish people a "good one" and they are free to apply that to whatever event or timescale they think is relevent. This is suitable to almost all occasions, and even helps prevent me from accidentally wishing them something awkward, like a good meal when I'm the one eating.

Actually in Greek (I don't speak Greek just have a bunch of Greek colleagues) they say good day but also good week and good month.

So, you get emails beginning "Dear RP, kalimera kai kali evdomado kai kalo mina."

I vaguely remember a skit where they just list longer time durations, maybe key and Peele?