sof
This method returns the latest zman krias shema (time to recite Shema in the morning) according to the opinion of the Magen Avraham (MGA) based on alos being 18˚ before sunrise. This time is 3 shaos zmaniyos (solar hours) after dawn based on the opinion of the MGA that the day is calculated from dawn to nightfall with both being 18 below sunrise or sunset. This returns the time of 3 * shaahZmanis18Degrees after dawn.
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.