[235 arcsine 1/[2*19]]/12=29d 12h 44m 25s
765433/25920=29d 12h 44m 33s
To calculate lunar phase dates for a given Longitude
Example, on 14th [d] April [m], 2010 [Y] the Moon is in Syzygy, in the Gregorian calendar.
Y modulo 100=R
R modulo 19=r
If r is greater than 9, r=N; If not, r-19=N
11N modulo [1447/49] = T,
[Y-R] modulo 19+3=s; if s=3, s=4
T-s+d+m = t;
Determine the Moon phase from the resulting number (P) using the following phases & event calculations.
: t + ⅔ + Longitude/15= New Moon Phase.
The Crescent is not visible for fifteen to sixteen hours before & after
the Syzygy: ⅔ of a day either side. If sunset be very close to that time, the Crescent will not be visible until the Sun is 5 degrees below the Horizon.
Calculate for a Syzygy (NM) as 0, New Moon as ⅔; & a Full Moon (FM) as 59/4. The other phases are multiples of 59/16.