How can I calculate the moon phase for LaTeX calendar?
My start point is D.E.Knuth's algorithm to calculate Easter is applied here https://texample.net/tikz/examples/birthday-calendar/
The number E is the epact, which specifies when a full moon occurs. However, I don't know how to access the variable \l_easter_E_int
If I could access E, then full moon would happen around 29 days after E.
Easter=-3, % Maundy Thursday Easter=-2, % Good Friday Easter, % Easter Sunday Easter=1, % Easter Monday Easter=39, % Feast of the Ascension Easter=49, % Pentecost Easter=50, % Whit Monday
Seems to be an easy way to state days with respect to "Easter". I don't know how this command works.
But instead of Easter=1, Easter=29,
How can I make the reference Epach=1, Epach=29, etc.?