12/Historical Note

Historical Note on $12$ (Twelve)
There are many occurrences of the number $12$ in various cultures in history:


 * There are $12$ months in a year, divided into $4$ seasons of $3$ months each.


 * There are $12$ signs of the Zodiac, divided into $3$ sets of $4$ each, and categorising them another way, into $4$ sets of $3$ each.


 * There are $12$ hours in each day and in each night.


 * There are $12$ semitones in an octave of a well-tempered scale.


 * There were $12$ pence in $1$ shilling in pre-decimal British coinage.

The word dozen, now falling into disuse, means a set of $12$.

Also see

 * Definition:Duodecimal Numbers