All
time is
divided into
six parts:
Morning, from 6 AM until 10 AM;
Midday, from 10 AM until 2 PM;
Afternoon, from 2 PM until 6 PM;
Evening, from 6 PM until 10 PM;
Gweepning, from 10 PM until 2 AM; and
Oh-my-god-what-are-we-doing-up-this-late-ning, from 2 AM until 6 AM.
See also Undocumented Features, from whence cometh this wonderful scheme.