How do I create a life/energy based system?

How do I create a life/energy based system where if the player life/energy reaches ‘0’ he/she can’t play the game and have to wait until it respawns. I would prefer it will not be affected by player changing his date & time settings:>

If you don’t want a local clock based system you need to check with online clock or run a server people need to log in. Then just on bool energy > desired enery value, let player play.