Searched and couldn't find anything, though I'm sure it's been addressed. When a flight has a departure time changed day of (for weather, traffic or what have you), when is it "official" (ie: the plane is not going to leave before then) vs. "modifiable" (plane could leave sooner if possible). Reason being, if I get an email that my flight is 60min delayed, I'd much rather spend that time at home and leave for the airport later as opposed to getting to the airport on time and hanging around. I've had it happen where a flight was delayed due to weather at the destination and had the flight be delayed 60min but then it was cut to 20min and we rushed to make a small window that ATC gave us. Fortunately I was at the airport when this happened but if I got that original 60min delay and waited I might have missed the flight even though I was "on time" per the revised time.