sof
This method returns Rav Moshe Feinstein's opinion of the calculation of sof zman tfila (zman tfilah (the latest time to recite the morning prayers)) according to the opinion of the GRA that the day is calculated from sunrise to sunset, but calculated using the first half of the day only. The half a day starts at sunrise and ends at fixed local chatzosfixedLocalChatzos]. Sof zman tefila is 4 shaos zmaniyos (solar hours) after sunrise or 2/3 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.
See also
.getFixedLocalChatzosBasedZmanim