tzais50
Method to return tzais (dusk) calculated as 50 minutes after sea level sunset. This method returns tzais (nightfall) based on the opinion of Rabbi Moshe Feinstein for the New York area. This time should not be used for latitudes different than the NY area.
Return
the Date representing the time. 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.