Lunar calendar support

[Haxxer]

Description

Lunar calendars are weird, and may need a different calculation approach compared to normal calendars. Normal calendars have a set number of days per month, while lunar calendars are driven by the moon's cycles. Eg. the month's length is the amount of days it takes for the moon to go from full moon to the next full moon, which may vary month to month.

[tctlrd]

I am using Fantasy Calander for a biblical calendar which of course follows the earth's lunar month. Alternating 30/29 day months works for the most part. A more purist way to generate months would be interesting. The year is a solar one though. So having these come together is where it gets a little tricky. The new year hinge is the Vernal Equinox. Inserting a 13th leap moon/month every 2-3 years is the current tradition to keep moons and sun in sync with spring. Currently the practice is a 19 year cycle containing seven leap years. This has issues though and is drifting the new year into the summer.
This calendar is the most eligant solution I have seen:
http://individual.utoronto.ca/kalendis/hebrew/rect.htm
https://calendars.fandom.com/wiki/Rectified_Hebrew_calendar

I would like to see this visualized with Fantasy Calendar.