Run a game while not in use on android

So, I'm making a game that needs to have things that happen after a given amount of time, for example, a plant needs to be growing, even if you are not playing the game. What would be the best way to approach this?

The best way would be, if your game already expects the player to be connected to the internet, check with a server to get the time.

Alternatively you could check the local time on the device, though, user can move their phone clock forward and back as they please.

Those are the methods I could think of.

The best way would be, if your game already expects the player to be connected to the internet, check with a server to get the time.

Alternatively you could check the local time on the device, though, user can move their phone clock forward and back as they please.

Those are the methods I could think of.

I'd imagine that issue with the second problem, what method would you recommend to check a server?