I'd imagine that if it was really that close then it would be a draw.
Checkmate as time expires
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The instant the checkmate move is completed - ie when the piece is released, the game is ended with checkmate even if the flag drops. If the flag falls before the move is completed then it is a loss on time. Both events would have to occur at exactly the same moment of time for there to be a problem. In practice the checkmate is there to see on the board while the flag fall isnt - the rule states that the flag is deemed to have fallen when it is seen to have fallen by the opponent or arbiter. I dont see in practice how a flag fall and releasing a piece can be seen to occur at exactly the same moment in time. Either the players would agree a draw or, if an arbiter was asked he would go with the checkmate
Thanks quequeg.
If the flag has fallen before the checkmate move is made but opponent haven't pointed that out then checkmate is valid. If the opponent points out that your time is up before you have made your move to checkmate then it's loss (or draw if there is no material enough). My inner lawyer is wondering that when you touch your piece it is considered a move then if I have picked up a piece and my opponent shouts:"TIME!" can I complete my move that is considered alrealy made and win the game if it's checkmate after that.
This move is considered to be made when you touch your piece comes from the rules where opponent makes a wrong move. Chess rules say that you have rigth to point out wrong move before you have made your own next move and touching a piece is considered as will to complete move and counts as move. So you have to point out that your opponent has made wrong move before you touch any piece.
I had this exact situation occur in a speed chess tournament in 1991. I picked up my queen, my opponent yelled "time" and I put my queen down right where I intended for it to go, checkmating him.
After much discussion, and a phone call by the TD to Walter Browne for advice, the TD ruled that my opponent did not have to stop the clocks in order to claim a win on time, which was the basis for my claim of a win.
Because I agreed that he yelled time before my hand released the piece, the TD ruled I could not claim checkmate, so it was a win for my opponent.
Then a spectator pointed out that my opponent only had a bare king and was not entitled to claim a win. After some additional discussion the TD altered his ruling to declare it a draw.
Under USCF rules for a regular tournament game the ruling might be different. The TD's call was made to Walter Browne because at the time Walter was president of a speed chess organization and the tournament I was competing in was using that organization's rules.
Hi guys, just for you to know it has just happened in one of my games here in chess.com.
I was running out of time, and my checkmate was exactly at zero time, but the game judged I´ve lost the game by lack of time. very frustrating! But this was weird because it seems the system was able to compute my movement, but had not enough time to compute my victory (the two things happened at the very same time, but it seems the system can´t process paralell tasks, so it needs to process one process at a time, and since it took some 0.0001 seconds between one and another, it just didn process my victory. I can assure it becasue the movement is registered and recorded in the post-analysis board, so this was considered a complete movement (I´ve already had the experience of run out time while I didn´t released the piece, and this incomplete movement is obviously not computed). 
Desconfusao wrote:
Hi guys, just for you to know it has just happened in one of my games here in chess.com.
I was running out of time, and my checkmate was exactly at zero time, but the game judged I´ve lost the game by lack of time. very frustrating! But this was weird because it seems the system was able to compute my movement, but had not enough time to compute my victory (the two things happened at the very same time, but it seems the system can´t process paralell tasks, so it needs to process one process at a time, and since it took some 0.0001 seconds between one and another, it just didn process my victory. I can assure it becasue the movement is registered and recorded in the post-analysis board, so this was considered a complete movement (I´ve already had the experience of run out time while I didn´t released the piece, and this incomplete movement is obviously not computed).
https://www.chess.com/game/live/12261365249
Your move did not make it to the server before your time ran out. The server keeps the official times but the client will not know if the move was made fast enough until the server computes the total time taken after accounting for lag.
This also happened to my game.
Check out this #chess game: jamesjosephmcdevitt vs Tyra928 - https://www.chess.com/live/game/74457105863
I checkmated my opponent and yet it recorded MY WIN on time!! Or did I miss something?
https://www.chess.com/game/1b5582f9-ea52-11ed-aa61-78701501000f
andriworld wrote:
I checkmated my opponent and yet it recorded MY WIN on time!! Or did I miss something?
https://www.chess.com/game/1b5582f9-ea52-11ed-aa61-78701501000f
Your link is completely broken. That is not how a game link looks like on chess.com at all.
This almost happened to me recently and it got me to thinking - What would happen if checkmate and time expiring for the player delivering mate happened at exactly the same moment? Is there an official rule on this?
If not, I sure wouldn't want to be an official monitoring the game and having to make the call.