How EASA night time is calculated

Under EASA rules, night is the period between the end of evening civil twilight and the beginning of morning civil twilight. Civil twilight ends when the centre of the sun's disc is 6° below the horizon.

Why it isn't that simple

The end of twilight depends on place and date. Flying east late in the day, night comes sooner than at the departure aerodrome; flying west, it recedes. You need the aircraft position at every moment.

Geardown's method

Geardown takes the off-block, takeoff, landing and on-block times. Before takeoff the aircraft is at the departure aerodrome; after landing, at the arrival aerodrome. In between it follows the great circle at constant speed. For every minute, Geardown computes the sun elevation at the estimated position and counts the minute as night when it is below −6°.

The result goes in the “Night” column of the EASA logbook. Takeoffs and landings are classified day or night from the sun elevation at the exact time and place.

What if my flight didn't follow the great circle?

The difference is usually a few minutes at most. You can always enter night time manually: your value replaces the automatic calculation.