Changing Guest Password Monthly

I have a small motel which has a hotspot. I want a hotspot user called guest. I want the password to change every month. I was thinking running a script hourly like so:

If month(in central time) = “01” or january
guest password = “janpass34”

If month(in central time) = “02” or february
guest password = “febpad27”

… and so on.

Has anyone done this or know how too?

Matt