How can I make an Idle Tycoon like incrementation over time, without having the game open

Hello!

I’m trying to figure out how to create an Idle incrementation like the one in games like Adventure Capitalist.

I was thinking about some math based on the time and date, but not sure if it’s worth trying, and not sure if Unity has some features linked to this.

Any kind of help, links, courses are greatly appreciated!

at least you can save data (between runs), so then could check previous saved date for example.

then there is this issue, and some ideas:

Thanks, brother!