Class: Hebruby::HebrewDate

Inherits:
Object
  • Object
show all
Defined in:
lib/hebruby.rb

Constant Summary collapse

HEBREW_EPOCH = 
347995
MONTH_NAMES = 
%w{none Nissan Iyar Sivan Tamuz Av Elul Tishrei Chesvan Kislev Tevet Shvat Adar} + ["Adar Sheni"]
HEB_MONTH_NAMES = 
[ nil, 'ניסן', 'אייר', 'סיון', 'תמוז', 'אב', 'אלול', 'תשרי',
'חשון', 'כסלו', 'טבת', 'שבט', 'אדר', 'אדר א\'', 'אדר ב\'']
HEB_DAYS = 
[ nil, 'א\'', 'ב\'', 'ג\'', 'ד\'', 'ה\'', 'ו\'', 'ז\'', 'ח\'', 'ט\'',
'י\'', 'י"א', 'י"ב', 'י"ג', 'י"ד', 'ט"ו', 'ט"ז', 'י"ז', 'י"ח',
'י"ט', 'כ\'' , 'כ"א', 'כ"ב', 'כ"ג', 'כ"ד', 'כ"ה', 'כ"ו', 'כ"ז','כ"ח', 'כ"ט', 'ל\'' ]
ONES = 
[ '', 'א', 'ב', 'ג', 'ד', 'ה', 'ו', 'ז', 'ח', 'ט' ]
TENS = 
[ '', 'י', 'כ', 'ל', 'מ', 'נ', 'ס', 'ע', 'פ', 'צ' ]

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*params) ⇒ HebrewDate

Constructor. When passed 1 parameter, the one parameter must either be an integer representing a Julian day number, or some kind of date object (e.g. Ruby’s Date class) that responds to the jd method to expose a Julian day number. When passed 3 parameters, they are day,month,year of the Hebrew date, as integers.



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# File 'lib/hebruby.rb', line 50

def initialize(*params)
  if params.size == 3
    @hd = params[0]
    @hm = params[1]
    @hy = params[2]
    convert_from_hebrew
  elsif params.size == 1
    jd=params[0]
    if jd
      if jd.is_a? Integer
        @jd = jd
      elsif jd.respond_to? :jd
        @jd = jd.jd
      else
        raise ArgumentError
      end
      convert_from_julian
    end
  else
    raise ArgumentError
  end
end

Instance Attribute Details

#hd ⇒ Object

Accessors for base Hebrew day, month, and year



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# File 'lib/hebruby.rb', line 41

def hd
  @hd
end

#hm ⇒ Object

Accessors for base Hebrew day, month, and year



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# File 'lib/hebruby.rb', line 41

def hm
  @hm
end

#hy ⇒ Object

Accessors for base Hebrew day, month, and year



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# File 'lib/hebruby.rb', line 41

def hy
  @hy
end

Class Method Details

.days_in_prior_years(year) ⇒ Object 



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# File 'lib/hebruby.rb', line 198

def self.days_in_prior_years(year)
  months_elapsed = (year - 1) / 19 * 235 + # Months in complete cycles so far
    12 * ((year - 1) % 19) + # Regular months in this cycle
    (1 + 7 * ((year -  1) % 19)) / 19 # Leap months in this cycle
  parts_elapsed = 204 +  793 * (months_elapsed % 1080)
  hours_elapsed = 5 +
    12 * months_elapsed +
    793 * ( months_elapsed / 1080) +
    parts_elapsed / 1080
  parts = 1080 * (hours_elapsed % 24) + (parts_elapsed % 1080)
  day = 1 + 29 * months_elapsed + hours_elapsed / 24

  if parts >= 19440 or #If the new moon is at or after midday,
    ( day % 7 == 2 and #...or is on a Tuesday...
      parts >= 9924 and # at 9 hours, 204 parts or later...
      not leap?(year) # of a common year
    ) or
    ( day % 7 == 1 and #...or is on a Monday...
      parts >= 16789 and # at 15 hours, 589 parts or later...
      leap?(year - 1) # at the end of a leap year
    )
  then
    day += 1 #then postpone Rosh HaShanah one day
  end

  #If Rosh HaShanah would occur on Sunday, Wednesday, or Friday
  #Then postpone it one more day
  day += 1 if [0,3,5].include?(day % 7)

  return day + HEBREW_EPOCH + 1
end

.heb_number(num) ⇒ Object

Return the representation in hebrew letters for a number less than 100

Raises:

  • (ArgumentError) 


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# File 'lib/hebruby.rb', line 131

def self.heb_number(num)
  raise ArgumentError if num>100 or num < 0
  return 'ט"ו' if num == 15
  return 'ט"ז' if num == 16
  if num < 10
    return '"' + ONES[ num % 10 ]
  elsif num % 10 == 0
    return '"' + TENS[ num / 10 ]
  else
    return TENS[ num / 10 ] + '"' + ONES[ num % 10 ]
  end
end

.jd_to_hebrew(jd) ⇒ Object

Convert Julian day number to Hebrew date This works by making multiple calls to to_jd, and is this very slow



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# File 'lib/hebruby.rb', line 258

def self.jd_to_hebrew(jd)
  greg_date = Date.jd(jd)
  month = [nil,9,10,11,12,1,2,3,4,7,7,7,8][greg_date.month]
  day = greg_date.mday
  year = 3760 + greg_date.year

  year += 1 while jd >= to_jd(year + 1, 7, 1)
  length = year_months(year)
  month = (1 + month % length) while jd > to_jd(year,month,month_days(year,month))

  day = jd - to_jd(year,month,1) + 1

  return [year, month, day]
end

.leap?(year) ⇒ Boolean

Is a given Hebrew year a leap year ?

Returns:

  • (Boolean) 


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# File 'lib/hebruby.rb', line 145

def self.leap?(year)
  return ((year * 7) + 1).modulo(19) < 7
end

.month_days(year, month) ⇒ Object

How many days are in a given month of a given year



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# File 'lib/hebruby.rb', line 161

def self.month_days(year, month)
  # First of all, dispose of fixed-length 29 day months
  case
    when (month == 2 || month == 4 || month == 6 || month == 10 || month == 13)
      return 29

    # If it's not a leap year, Adar has 29 days
    when (month == 12 && !leap?(year)) then
      return 29

    # If it's Cheshvan, days depend on length of year
    when month == 8 && year_days(year).modulo(10) != 5 then
      return 29

    # Similarly, Kislev varies with the length of year
    when (month == 9 && (year_days(year).modulo(10) == 3)) then
      return 29

    # Nope, it's a 30 day month
    else
      return 30
  end
end

.to_jd(year, month, day) ⇒ Object

Convert hebrew date to julian day number



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# File 'lib/hebruby.rb', line 231

def self.to_jd(year, month, day)
  months = year_months(year)

  jd = day

  if (month < 7) then
    for mon in 7..months
      jd += month_days(year, mon)
    end

    for mon in 1...month
      jd += month_days(year, mon)
    end
  else
    for mon in 7...month
      jd += month_days(year, mon)
    end
  end

  jd += days_in_prior_years(year)

  return jd
end

.year_days(year) ⇒ Object

How many days are in a Hebrew year ?



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# File 'lib/hebruby.rb', line 156

def self.year_days(year)
  return to_jd(year + 1, 7, 1) - to_jd(year, 7, 1)
end

.year_months(year) ⇒ Object

How many months are there in a Hebrew year (12 = normal, 13 = leap)



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# File 'lib/hebruby.rb', line 151

def self.year_months(year)
  return leap?(year) ? 13 : 12
end

Instance Method Details

#convert_from_hebrew ⇒ Object

internal conversion method to keep fields syncronized with julian day number



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# File 'lib/hebruby.rb', line 194

def convert_from_hebrew
  @jd = HebrewDate.to_jd(@hy, @hm, @hd)
end

#convert_from_julian ⇒ Object

internal conversion method to keep fields syncronized with julian day number



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# File 'lib/hebruby.rb', line 186

def convert_from_julian
  dateArray = HebrewDate.jd_to_hebrew(@jd)
  @hy = dateArray[0]
  @hm = dateArray[1]
  @hd = dateArray[2]
end

#day ⇒ Object 



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# File 'lib/hebruby.rb', line 73

def day
  return @hd
end

#heb_date ⇒ Object

Provide Hebrew display date



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# File 'lib/hebruby.rb', line 121

def heb_date
  return heb_day_name + " ב" + heb_month_name + " " + heb_year_name
end

#heb_day_name ⇒ Object

Provide Hebrew day of the month, in hebrew letters.



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# File 'lib/hebruby.rb', line 107

def heb_day_name
  return HEB_DAYS[@hd]
end

#heb_month_name ⇒ Object

Provide Hebrew month name in Hebrew letters



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# File 'lib/hebruby.rb', line 98

def heb_month_name
  if HebrewDate.leap?(@hy) and @hm >= 12 # leap year and from adar
   return HEB_MONTH_NAMES[@hm + 1]
  else
   return HEB_MONTH_NAMES[@hm]
  end
end

#heb_year_name ⇒ Object

Provide Hebrew year number in hebrew letters

Raises:

  • (RangeError) 


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# File 'lib/hebruby.rb', line 112

def heb_year_name
  year = @hy
  raise RangeError, "only 5700 - 5899 supported" if year < 5700 || year >= 5900
  prefix = year / 100 == 57 ? "התש" : "התת"
  suffix = HebrewDate.heb_number(year % 100)
  full = prefix + suffix
end

#jd ⇒ Object

return julian day number



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# File 'lib/hebruby.rb', line 88

def jd
  return @jd
end

#julian_date ⇒ Object

return Ruby ‘Date` object



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# File 'lib/hebruby.rb', line 126

def julian_date
  return Date.jd(@jd)
end

#month ⇒ Object

Provide Hebrew transliterated month display name



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# File 'lib/hebruby.rb', line 78

def month
  return @hm
end

#month_name ⇒ Object

Provide Hebrew month name transiterated into Englsih



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# File 'lib/hebruby.rb', line 93

def month_name
  return MONTH_NAMES[@hm]
end

#year ⇒ Object

return Hebrew year



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# File 'lib/hebruby.rb', line 83

def year
  return @hy
end