I guess your talking about, 'off blocks time' this is the time that the chocks are removed from the aircraft and it starts to push back from the gate. This is called into the control centre by the aircraft dispatcher, and is used to say whether the flight left on time or not. The fact that it spent the next 30 minutes sitting on the taxi way is immaterial to the dispatcher.
As for wheels up time, never heard it been recorded, although all these sort of things are now recorded by the onboard computer so it may be noted by the airlines.
Aircraft I've flown: A300/A310/A320/A321/A330/A340/B727/B732/B733/B734/B735/B738/B741/B742/B744/DC10/MD80/IL62/Bae146/AR