When you sleep for 1/4 of the day, then are awake for another 1/4 of the day, then sleep again for 1/4 of the day, and then awake for the rest of the 1/4 of the day.
Example of neo nocturnal:
7pm-4am: awake 4am-7am- sleep 7am-3pm: awake
3pm-7pm: sleep