holidays/data/common_methods.yaml

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# Common method definitions for the Ruby Holiday gem.
# Updated 2008-11-21.
---
methods:
easter: |
# Get the date of Easter in a given year.
#
# +year+ must be a valid Gregorian year.
#
# Returns a Date object.
#--
# from http://snippets.dzone.com/posts/show/765
# TODO: check year to ensure Gregorian
def self.easter(year)
y = year
a = y % 19
b = y / 100
c = y % 100
d = b / 4
e = b % 4
f = (b + 8) / 25
g = (b - f + 1) / 3
h = (19 * a + b - d - g + 15) % 30
i = c / 4
k = c % 4
l = (32 + 2 * e + 2 * i - h - k) % 7
m = (a + 11 * h + 22 * l) / 451
month = (h + l - 7 * m + 114) / 31
day = ((h + l - 7 * m + 114) % 31) + 1
Date.civil(year, month, day)
end