2 definitions by Karl Palmen

yerm

In a lunar calendar, a period somewhat like a year in which the odd numbered months have 30 days and the even number months have 29 days.
Also the time it takes for the mean synodic month to fall half a day behind the 29.5 day cycle.

A lunar calendar can constructed from yerms of 17 and 15 months.

by Karl Palmen April 23, 2003

draconic

pertaining to the passage of the moon in its orbit through its nodes.

The draconic month is about 27.2122 days.

by Karl Palmen November 13, 2003