How do I make a time that seemingly counts when game is off?

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?

I would start with the rexrainbow plugin (https://dl.dropboxusercontent.com/u/577 ... _date.html ) to detect system date/time and I guess store the time on game exit and compare how long has passed when loading the game.

I guess you'll have to make use of local storage for save game data :

https://www.scirra.com/manual/188/local-storage

Or you can use a time API to retrieve time from a server.

Speaking of server, tt seems like the only foolproof way to make a game like that is to store some info on a server.

Yea, sadly. JavaScript is very, VERY manipulable.

Yea, sadly. JavaScript is very, VERY manipulable.

gumshoe2029

Any client application that depends on system time is manipulable

I remember changing time in the BIOS to bypass parental control when I was a kid

Yea, like EA's Dragon Age: Inquisition can be hacked in that way too.