1st astral moon is January, 1st umbral moon is febuary, 2nd astral moon is march, 2nd umbral moon is april... and "sun" is each day.

So, for example, my nameday is the 8th sun of the third umbral moon. This means mine is the 8th of June.

Also, each month has a given guardian. For June, it's Oschon the Wanderer.