bain
This method returns the beginning of bain hashmashos of Rabbeinu Tam calculated according to the opinion of the Divrei Yosef (see Yisrael Vehazmanim) calculated 5/18th (27.77%) of the time between alos (calculated as 19.8 before sunrise) and sunrise. This is added to sunset to arrive at the time for bain hashmashos of Rabbeinu Tam.
Return
the Date of bain hashmashos of Rabbeinu Tam for this calculation. If the calculation can't be computed such as northern and southern locations even south of the Arctic Circle and north of the Antarctic Circle where the sun may not reach low enough below the horizon for this calculation, a null will be returned. See detailed explanation on top of the AstronomicalCalendar documentation.