The word Month , Moonth or “Monath” as the Old English said, comes from
the word “Moon”.
To the Anglo-Saxon Heathens, each month began on the night that the FIRST CRESCENT of the Moon appeared. The night of
the new moon is the first night of the New Month. As soon as that little
sliver of a moon appears, that is the first day of the Month. The Full
moon would be the middle of the month, and when the moon disappears, the
month is over- but the new month does not begin properly until the new
sliver of moon appears in the sky.
The old English word “Monath” is where we get the word “Month”. For example Blotmonath=November, Haligmonath=September.
The Intercalary Month, or the Thirteenth Moon.
A normal year will have 12 months- but every so often, you will have the heathen equivalent of a “Leap Year”- a special
month will appear, making thirteen months for that year. The intercalary
month on the heathen calendar is called THORNRILITHA. It means Third
A year that has a Thornrilitha or an intercalary month is called a Thrilitha year, or a year of Three Lithas.
If the first Crescent Moon that begins the Month of Afterlitha appears on
or before July 4th, then the next month- the month that follows
Afterlitha will be the Intercalary month. So every year, when the month
of Afterlitha begins, you will know if the next month will be the normal
next month, or if it will be the intercalary.
Another way to work it is to look at Foreyule & Aefteryule.
If the 1st Crescent Moon that begins the Month of Aefteryule is seen during the
Mothernights or the eve of Yule, anywhere from the Solstice to Jan 4th,
then we will have a Thrilitha year following.