bain
This method returns the beginning of Bain hashmashos of Rabbeinu Tam calculated as a 58.5 minute offset after sunset. bain hashmashos is 3/4 of a Mil before tzais or 3 1/4 Mil after sunset. With a Mil calculated as 18 minutes, 3.25 * 18 = 58.5 minutes.
Return
the Date of 58.5 minutes after sunset. If the calculation can't be computed such as in the Arctic Circle where there is at least one day a year where the sun does not rise, and one where it does not set, a null will be returned. See detailed explanation on top of the AstronomicalCalendar documentation.