Persona Like Calendar System?

I’m working on a project kinda like the Persona series. Right now I’m tasked with programming the calendar system. In which days pass as you play the game, and the current day/month are marked on a in game calendar. Events will take place on certain days and so on. I don’t really know where to start with this. Anyone have any tutorials, or just general advice?

Maybe have a variable that will add 1 when a day passes and if a certain number passes into the variable, format the variable and add a 1 to a month variable?