Source code for date

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""Calculate spacial dates.

:Date: 2018-01-15

.. module:: date
  :platform: *nix, Windows
  :synopsis: Special dates.
   
.. moduleauthor:: Daniel Weschke <daniel.weschke@directbox.de>
"""

def gaußsche_osterformel(year):
  """Gaußsche Osterformel.

  :param year: the year to calculate the Easter Sunday
  :type year: int
  
  :returns: the day of Easter Sunday as a day in march.
  :rtype: int
  
  :ivar X: Das Jahr / year
  :vartype X: int
  :ivar K(X): Die Säkularzahl
  :vartype K(X): int
  :ivar M(X): Die säkulare Mondschaltung
  :vartype M(X): int
  :ivar S(K): Die säkulare Sonnenschaltung
  :vartype S(K): int
  :ivar A(X): Den Mondparameter
  :vartype A(X): int
  :ivar D(A,M): Den Keim für den ersten Vollmond im Frühling
  :vartype D(A,M): int
  :ivar R(D,A): Die kalendarische Korrekturgröße
  :vartype R(D,A): int
  :ivar OG(D,R): Die Ostergrenze
  :vartype OG(D,R): int
  :ivar SZ(X,S): Den ersten Sonntag im März
  :vartype SZ(X,S): int
  :ivar OE(OG,SZ): Die Entfernung des Ostersonntags von der Ostergrenze (Osterentfernung in Tagen)
  :vartype OE(OG,SZ): int
  :ivar OS(OG,OE): Das Datum des Ostersonntags als Märzdatum (32. März = 1. April usw.)
  :vartype OS(OG,OE): int
  
  Algorithmus gilt für den Gregorianischen Kalender.

  source: https://de.wikipedia.org/wiki/Gau%C3%9Fsche_Osterformel
  """
  x = year
  k = x // 100
  m = 15 + (3*k + 3) // 4 - (8*k + 13) // 25
  s = 2 - (3*k + 3) // 4
  a = x % 19
  d = (19*a + m) % 30
  r = (d + a // 11) // 29
  og = 21 + d - r
  sz = 7 - (x + x // 4 + s) % 7
  oe = 7 - (og - sz) % 7
  os = og + oe
  return os

def easter_sunday(year):
  """Easter Sunday.

  :param year: the year to calculate the Easter Sunday
  :type year: int
  
  :returns: the day of Easter Sunday
  :rtype: datetime.date"""
  import datetime
  march = datetime.date(year, 3, 1)
  day = march + datetime.timedelta(days=gaußsche_osterformel(year))
  return day

def easter_friday(year):
  """Easter Friday.

  :param year: the year to calculate the Easter Friday
  :type year: int
  
  :returns: the day of Easter Friday
  :rtype: datetime.date"""
  import datetime
  day = easter_sunday(year) + datetime.timedelta(days=-2)
  return day

def easter_monday(year):
  """Easter Monday.

  :param year: the year to calculate the Easter Monday
  :type year: int
  
  :returns: the day of Easter Monday
  :rtype: datetime.date"""
  import datetime
  day = easter_sunday(year) + datetime.timedelta(days=+1)
  return day

def ascension_of_jesus(year):
  """Ascension of Jesus.

  :param year: the year to calculate the ascension of Jesus
  :type year: int
  
  :returns: the day of ascension of Jesus
  :rtype: datetime.date"""
  import datetime
  day = easter_sunday(year) + datetime.timedelta(days=+39)
  return day

def pentecost(year):
  """Pentecost.

  :param year: the year to calculate the Pentecost
  :type year: int
  
  :returns: the day of Pentecost
  :rtype: datetime.date"""
  import datetime
  day = easter_sunday(year) + datetime.timedelta(days=+49)
  return day