A calendar
blue moon yes
The moon has some wonderful Medieval names, as it occurs each month:
January: The Wolf Moon
February: The Storm Moon
March: The Chaste Moon
April: The Seed Moon
May: The Hare Moon
June: The Dyan Moon
July: The Mead Moon - Earth hart would like that one
August: The Corn Moon
September: The Barley Moon
October: The Blood Moon
November: The Snow Moon
December: The Oak Moon
The
Moon Names site has others from around the world. Very beautiful names they are too.
Forgive me, I digress... back to the Blue Moon
Blue Moon Facts - On Average:
* Blue Moons occur once every 2.7 years.
* 7 times every 19 years.
* Once every 33 months.
* 37 times every century.
* Once every 33 full moons.
(info from the site above)