I tested it and yes, it is possible to circumvent the system by changing the time of the PC or the phone.
How can I fix this problem?
If the problem is resolved I will buy.
Yes I'm aware of this. This only can be avoided if you sync the reward with an external time server.
This template uses rexrainbow TimeAwayL plugin. This plugin saves a time stamp in the localstorage.
And my template is comparing that time stamp with the current device time.
Therefor if you change the time on the device, you can manipulate the reward system.
At the moment the only way I see to fix that, is to not compare the time with the device time, but with an external server time.
But for this an internet connection is mandatory.