The time added is corroborated here. http://www.chess.com/forum/view/suggestions/new-auto-vacation-rule
"This is to prevent "vacation" time being used to just manage an over-loaded games list. - but removal of 24 hours from vacation time, in turn adds 24 hours onto the game clock, hence the time difference. One day is still lost from vacation time though.".
Thank you TadDude for clearing this vacation thing up.
The time added is corroborated here. http://www.chess.com/forum/view/suggestions/new-auto-vacation-rule
"This is to prevent "vacation" time being used to just manage an over-loaded games list. - but removal of 24 hours from vacation time, in turn adds 24 hours onto the game clock, hence the time difference. One day is still lost from vacation time though.".
Thank you TadDude for clearing this vacation thing up.
I see a member making these proclamations but not a member of staff. If a member of staff has said these things then please supply link/post #.
If you have a way of accessing Ticket 163335, you will find the response that I noted in my earlier post. That is the only thing that I have seen from the staff on this topic.
If you have a way of accessing Ticket 163335, you will find the response that I noted in my earlier post. That is the only thing that I have seen from the staff on this topic.
Okay, thanks.
I posted a month or so ago somewhere or other about the same problem Reb noticed. This is the first explanation I've seen about how my opponent was repeatedly able to keep bumping his game clock back to 3 full days after it had run down to nearly 2 days. He did that 4 times in one turn after I was up by a Queen and 3 pawns over his remaining King and 2 pawns. And then after all that stalling he finally just let his time expire rather than make another useless move. I hadn't realized until now that chess.com made it that way intentionally. I don't mind people stalling when they're losing, but it doesn't seem right that they should be able to maneuver and add time to their actual game clock in CC.
@kco
Yes, I noticed too that chessocity got a premium membership, so that probably means that his clock hacking arguments were valid. As far as I can tell, he strictly has experience in bullet chess, but it sounds like his packet hacking technique would work for other time controls including turn-based. So over and above this vacation-time question, it seems like turn-based clock hacking could also be taking place.
Chessocity's original post on clock hacking can be found here.
As far as what's being done about it...I'm just as much in the dark as you are.
Is there a practical need for clock hacking in turn-based chess?
I don't think so, maybe one could think of few potential situations where it could make a difference(annoying an opponent, stalling the game, ...) , but usually you have enough time to play to move. 
I agree-- in CC any clock "hacking" would seem to be for annoyance purposes, not for gaining any edge. After all, if the person has the time to devote to performing the hack, they could just as easily be making the move. The additions of time that Reb and I noticed for our opponents appear to be simply a matter of knowing about and employing a feature already present in the system (although whether the feature is present by design or by accident isn't real clear).
I'm pretty sure that there is a bug in CC that makes the clocks increase in time slightly, so that at times I've had 7 hours left on a game, and refreshed a bit later to see the game at 8 hours.
I've seen those little increments on a couple of my own games, but usually it's when my main games page will show x hours left and when I actually go to that game board it will say I have x+1 hours left.
But this other snafu involves large amounts of time. In a 3-day/turn game, my opponent was able to add a total of more than 3 additional days to one of his turns by repeatedly getting his clock refreshed all the way back to the full 3 day mark. His clock actually counted down through more than 6 days during one "3-day" move.
In any case, Erik and CC are not responding to anyone's posts in this thread. With the membership in place, it would seem that they have agreed not discuss the details of a real exploit any further.
Despite all that has been said about his original concern, chessocity now has "street cred." Not bad for someone who has only been a member of chess.com for just one week!
Respect! 
Expensive lesson for erik, lifetime Diamond membership soon racks up.
Think of the movie, "Thank You for Smoking." Someone's addiction will pay for all their expenses.
In any case, Erik and CC are not responding to anyone's posts in this thread. With the membership in place, it would seem that they have agreed not discuss the details of a real exploit any further.
Despite all that has been said about his original concern, chessocity now has "street cred." Not bad for someone who has only been a member of chess.com for just one week!
I would agree. Chessocity (and chessroboto for that matter) does have street cred, and chessocity said, "Sadly, there are clock hackers out there and they are abundant."
Straight from a staffer!
What else will forum peeps ask for about the clock hack (short of your own lifetime Diamond or how its done)?
EDIT
Thanks, Erik. That's reassuring since I'm going to be starting Live Chess again soon.
Amy
Thanks, Erik. That's reassuring since I'm going to be starting Live Chess again soon.
Amy
Sounds good !
Excellent, this thread turn out better than i thought it would be. Thank you erik for your answers not only for me but also for the community.
When the vacation policy was changed, the following feature was added for premium members: if auto timeout protection activates and the member turns vacation off before 24 hours has elapsed, the remaining time is added to their clocks. This wasn't announced. I found out about it after contacting support when one of my opponent's time increased several hours without their having made a move.
This is all very confusing ! I thought if your auto vacation protection kicks in you are charged for 24 hours MINIMUM ?! Now you say if they turn it off before its been 24 hours they get time added back to their clock ?! HHmmmmmmmm I didnt know CC chess has increments !? I dont see why a member would ever have time added back to his clock in CC chess ?!
Neither do I, however it's not entirely clear whether this turn of events was intended or if it's a bug which will be sorted out.