Proposal: Yet another Date method

ruby-talk
1

Hi,

I would like the Date class to be extended by this:

  require "date"
  
  class Date
    class <<self
      def easter_western year
        # This is after Donald E. Knuth and it works for both
        # Julian (before 1583) and Gregorian (after 1582) calendars.
        g = year%19 + 1 # golden number
        c = year/100 + 1 # century
        x = (3*c/4) - 12 # corrections
        z = (8*c+5)/25 - 5
        d = 5*year/4 - x - 10 # March((-d)%7)th is Sunday
        e = (11*g + 20 + z - x) % 30 # moon phase
        e += 1 if e == 25 and g > 11 or e == 24
        n = 44 - e # full moon
        n += 30 if n < 21
        month = 3
        day = n+7 - (d+n)%7
        if day > 31 then
          month += 1
          day -= 31
        end
        civil year, month, day
      end
      alias easter easter_western
    end
  end

I tested it with all easter date tables I found on the web
in German, English and French.

Happy Easter!

Bertram

···

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de

2

Bertram Scharpf <lists@bertram-scharpf.de> writes:

Hi,

I would like the Date class to be extended by this:

cf. ruby-1.8.6/sample/goodfriday.rb

···

Happy Easter!

Bertram

--
Christian Neukirchen <chneukirchen@gmail.com> http://chneukirchen.org

3

If we are taking a vote on this I vote YES

···

On Sun, 2007-04-08 at 22:05 +0900, Bertram Scharpf wrote:

Hi,

I would like the Date class to be extended by this:

  require "date"
  
  class Date
    class <<self
      def easter_western year
        # This is after Donald E. Knuth and it works for both
        # Julian (before 1583) and Gregorian (after 1582) calendars.
        g = year%19 + 1 # golden number
        c = year/100 + 1 # century
        x = (3*c/4) - 12 # corrections
        z = (8*c+5)/25 - 5
        d = 5*year/4 - x - 10 # March((-d)%7)th is Sunday
        e = (11*g + 20 + z - x) % 30 # moon phase
        e += 1 if e == 25 and g > 11 or e == 24
        n = 44 - e # full moon
        n += 30 if n < 21
        month = 3
        day = n+7 - (d+n)%7
        if day > 31 then
          month += 1
          day -= 31
        end
        civil year, month, day
      end
      alias easter easter_western
    end
  end

I tested it with all easter date tables I found on the web
in German, English and French.

Happy Easter!

Bertram

4

I wrote something that tests for Easter, Christmas, 4th of July, and
so on wrapped into a method called "is_national_holiday?" that I
planned on releasing as a gem, but I never did...I still have it if
you actually need something that doees this.

--Jeremy

···

On 4/8/07, Bertram Scharpf <lists@bertram-scharpf.de> wrote:

Hi,

I would like the Date class to be extended by this:

  require "date"

  class Date
    class <<self
      def easter_western year
        # This is after Donald E. Knuth and it works for both
        # Julian (before 1583) and Gregorian (after 1582) calendars.
        g = year%19 + 1 # golden number
        c = year/100 + 1 # century
        x = (3*c/4) - 12 # corrections
        z = (8*c+5)/25 - 5
        d = 5*year/4 - x - 10 # March((-d)%7)th is Sunday
        e = (11*g + 20 + z - x) % 30 # moon phase
        e += 1 if e == 25 and g > 11 or e == 24
        n = 44 - e # full moon
        n += 30 if n < 21
        month = 3
        day = n+7 - (d+n)%7
        if day > 31 then
          month += 1
          day -= 31
        end
        civil year, month, day
      end
      alias easter easter_western
    end
  end

I tested it with all easter date tables I found on the web
in German, English and French.

Happy Easter!

Bertram

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de

--
http://www.jeremymcanally.com/

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