How to protect yourself from forward arrows on mobile devices?

Question

Game development

The game has a lot of mechanics tied to timers. The game must be available offline.
Like when it's off!!! Internet on the device - protect yourself from moving the arrows of the device forward?

Answer 1

No way. Without a standard, you will not be able to distinguish the translation of the clock from the natural course of time. Let the cheater play offline as much as he wants, but during the next synchronization with the server, if you determine the fact of a clock change, you either completely roll back the game state to the one saved on the server, or withdraw individual rewards, it depends on the mechanics. You can simply assign the status of a cheater to the player and cut off all network interactions with other players, let him have fun as he wants, the main thing is not to interfere with others.

Answer 2

Without the Internet - nothing

Answer 3

Starting internal timer - sets the server by the UUID of the device, encrypts it and puts it next to the application.
Keep your timer inside the application with the necessary timeline.
1 second has passed timer++
another one has passed timer++
The clock change here is not very helpful.

Answer 4

And how do you connect timers with real time? There are not enough details for efficient (or not so) advice.