How can i make the game keep running in the background on android/ios ?

Hi
i’m working on a simulation game, like Sims and SimCity etc… where player builds a city or people whatever, and then comes back next day to get his income etc…please any help

It’s pretty simple, on launch you need to get the date using System.DateTime.now, compare it to a date you stored when the game last saved, and calculate the income for the time difference.