sof
This method returns Rav Moshe Feinstein's opinion of the calculation of sof zman krias shema (latest time to recite Shema in the morning) according to the opinion of the Magen Avraham (MGA) that the day is calculated from dawn to nightfall, but calculated using the first half of the day only. The half a day starts at alos defined as 90 minutes before sunrise and ends at fixed local chatzosfixedLocalChatzos]. Sof Zman Shema is 3 shaos zmaniyos (solar hours) after this alos or half of this half-day.
Return
the Date of the latest zman krias shema. 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.