Daddis At AOPA:
The same would be true on the other end of the day as well. To be legal, the flight with passengers would have to commence no earlier than one hour before sunrise. That is, engine start, not actual takeoff or departure time.
Where is that written? I see nothing to that effect in any FAA regulation -- not 61.57(b) or anything else in Part 61/91. Note that flight time for pilot purposes does not even begin until the aircraft first moves under its own power (14 CFR 1.1), which may occur long after engine start. AFAIK, the FAA has always held that day/night times for recent experience purposes are only an issue from takeoff to landing.