Yes....unless you have paused the game. Then it seems to depend on when you un-pause it. It seems to just count every 24 hours of play time.

example: You buy it at noon then pause it at 10 pm (10 hours of play). If you un-pause it at noon the next day, it should refill at 2 am (14 hours later).

That seems to be how it is working for me.