JAR mentions logboog rules in JAR FCL 1.080. Below is IEM FCL 1.080, which is the "Interpretive and Explanatory Material", found in part 2 of the JAR FCL:
1. JAR-FCL 1.080 and JAR-FCL 2.080 require holders of a flight crew licence to record details of all flights flown in a format acceptable to the National Aviation Authority responsible for licence or rating issue. This logbook enables pilot licence holders to record flying experience in a manner which will facilitate this process while providing a permanent record of the licence holders flying. Pilots who fly regularly aeroplanes and helicopters or other aircraft types are recommended to maintain separate logbooks for each type of flying.
2. Flight crew logbook entries should be made as soon as practicable after any flight undertaken. All entries in the logbook shall be made in ink or indelible pencil.
3. The particulars of every flight in the course of which the holder of a flight crew licence acts as a member of the operating crew of an aircraft are to be
recorded in the appropriate columns using one line for each flight, provided that if an aircraft carries out a number of flights upon the same day returning on each occasion to the same place of departure and the interval between successive flights does not exceed thirty minutes, such series of flights may be recorded as a
single entry.
4. Flight time is recorded from the time the aircraft first moves under its own power for the purpose of taking off until the time the aircraft finally comes to rest after landing (see JAR-FCL 1.001).
5. When an aircraft carries two or more pilots as members of the operating crew, one of them shall, before the flight commences, be designated by the operator as the aircraft ‘commander’, in accordance-with JAR-OPS, who may delegate the conduct of the flight to another suitable qualified pilot. All flying carried
out as ‘commander’ shall be entered in the log book as ‘pilot-in-command’. A pilot flying as ‘pilot-in-command under supervision’ or ’student pilot-in-command’ shall enter flying times as ‘pilot-in-command’ but all such entries shall be certified by the commander or flight instructor in the ‘Remarks’ column of the logbook.