Am assuming you mean he didn't accept a draw and won on time.
To be fair, if that is the case, he managed his time better than you and deserved his victory.
Chess played with time controls is a balance between the position on the board AND the clock.
I totally agree with you on that one but if both players have more than 10 seconds, I think its just a non-sportsmanlike thing to do.
Am assuming you mean he didn't accept a draw and won on time.
To be fair, if that is the case, he managed his time better than you and deserved his victory.
Chess played with time controls is a balance between the position on the board AND the clock.