What time zone is used for operating an airplane? This might be a silly question but my thinking was the following:

There has to be a definition of time in an airplane for the logging of data and so on, but what definition would that be assuming a flight goes across timezones?

Would it be the local time at the airport of departure? Or at that of arrival? or maybe even a third, commonly agreed upon time (e.g., GMT)?



The idea came from a story of a friend that was traveling with the ship from Italy (GMT+1) to Greece (GMT+2). The cafeteria on board had a sign saying that it opens at 14:00, but on 14:20 local Italy time, while the ship was anchored in Italy, he was denied service by the crew saying that the sign was referring to Greece local time; where the ship "belongs".
The pilot (and the ATC) use the UTC (Coordinated Universal Time). The flight's departure and arrival are in terms of the local times at the respective airports.

As for data logging, the FDR/CVR usually records in UTC (preferred) or the relative time count (usually count increments each 4 seconds of system operation). See Appendix M to Part 121 - Airplane Flight Recorder Specifications, for example.