Module: HebCal::Passover

Included in:
HolidaysHelper
Defined in:
lib/hebcal/passover.rb

Instance Method Summary collapse

Instance Method Details

#WhenIsPesach(yearG) ⇒ Object 



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# File 'lib/hebcal/passover.rb', line 6

def WhenIsPesach yearG
  _HPD = PassoverConstants::HALAKIM_PER_DAY
  _MZ = PassoverConstants::MOLAD_ZAQEN

  # CALCULATE MOLAD
  yearH = yearG + 3760
  year_in_julian_cycle = yearG % 4
  molad = PassoverHelper::CalculateMolad yearH
  halakim_into_day = molad % _HPD

  # CALCULATE CALENDAR DATE OF PESACH
  gregorian_divergence = (yearG/100).floor - (yearG/400).floor - 2
  pesach_julian_day = (molad - halakim_into_day) / _HPD

  day_of_week = ((3 * yearG) + (5 * year_in_julian_cycle) + pesach_julian_day) % 7
  pesach_day = pesach_julian_day + gregorian_divergence

  if [1,3,5].include? day_of_week then
    pesach_day += 1
  elsif (0 == day_of_week && !PassoverHelper::PrecedesLeapYear(yearH) && halakim_into_day >= PassoverConstants::TARAD + _MZ)
    pesach_day += 2
  elsif (6 == day_of_week && PassoverHelper::IsLeapYear(yearH) && halakim_into_day >= PassoverConstants::TUTAKPAT + _MZ)
    pesach_day += 1
  end

  pesach_month = 3

  pesach = Time.new(yearG, pesach_month, 1) + (pesach_day - 1) * 24 * 60 * 60
  pesach.dst? ? pesach - 60 * 60 : pesach
end