I am wanting to make a time based upgrade system for a game. I would like to know how, or be pointed into the right direction on how to make a timer that will seemingly count even if game is closed and can tell if device time has been changed.
I know you can do this by comparing the device time during game play and at start of game play and change accordingly, but not sure how to accomplish this.
Example: An hour timer is started. Player leaves game and does whatever with device. Player comes back in 55 minutes and timer has 5 minutes left. How do I achieve this and how do I detect if someone changed device time and/or daylight savings time clock change took place?