Just got pointed to this thread in IRC -- I've been playing the last few days but am out now as well.
To be fair, SuMguy isn't referencing the time he sent the money on his computer -- he is referencing the blockchain's timestamp, the same timestamp you referenced.
Even if he did send AFTER the game ended (which he didn't), your game still shows the game being active when it no longer is. This is an issue regardless of what time SuMguy sent the transaction.
I see the disclaimers in the FAQ but the entire game clock not being the actual time is pretty scammy sounding.
As others have suggested in this thread, you could be using blockchain's API -- I hope you'll take those suggestions into consideration and implement them.
To say that it is a gamble is not a fair statement, as there should still be certain rules that the game needs to abide by. If the clock is a lie, fix the clock or refund the person who lost out due to your shoddy implementation of it.
Anyways, I'm done with this game and I'd encourage other people who happen upon this thread to think twice before sending your coins to poncrypto until he can fix the system.