Suppose both players have 0 seconds left on the clock, but the clock indicates that the flag of player B has fallen first, which is claimed by Player A. Player A has enough material to mate his opponent (but also no time left, that is the point!) – has he just won the game?
The rules tell us (emphasisis by me):
(6.11) If both flags have fallen and it is impossible to establish which flag fell first then:
- The game shall continue if this occurs in any period of the game except the last period.
- the game is drawn if this occurs in the period of a game in which all remaining moves must be completed.
Therefore I think Player A has won. Sadly enough the rules do not explicitly tell what happens if is possible to establish which flag fell first (or at least I was unable to find that paragraph).