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Function to compute easter day. Pass a year as integer, get a serial date.

Function to compute easter day. Pass a year as integer, get a serial date.

Rate Function to compute easter day. Pass a year as integer, get a serial date.

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' Pass year as 4dgts number
' Returns a DateSerial
' VB translation from C by [email protected]

' Source:
' http://www.oremus.org/liturgy/etc/ktf/app/easter.html
' and its link to http://www.ely.anglican.org/etc/easter2.c

'           Simple EASTER date programme
'           ============================
' Computes the date of Easter, according to the Gregorian
' calendar (for years after 1752) or the Julian Calendar
' (for years before 1753).
' Simon Kershaw: 29.Jan, 1996, 2.Feb.1996.
'
'
'
'   Copyright (c) Simon Kershaw 1996. All rights reserved.
'   ================================= ====================
'     This code may be reproduced and used, without fee,
'     in part or in full provided the copyright notice and
'     these conditions are distributed with it.  No fee,
'     other than recovery of reasonable costs, may be
'     charged without explicit permission from the
'     author, Simon Kershaw, <[email protected]>.
'     All rights reserved.
'
'
'
' The date of Easter Day was defined by the Council of
' Nicaea in AD325 as the Sunday after the first full moon
' which falls on or after the Spring Equinox.  The
' Equinox is assumed to always fall on 21st March, so the
' calculation reduces to determining the date of the full
' moon and the date of the following Sunday.  The algorithm
' used here was introduced around the year 532 by Dionysius
' Exiguus.  Under the Julian Calendar a simple 19-year
' cycle is used to track the phases of the Moon.  Under the
' Gregorian Calendar (devised by Clavius and Lilius, and
' introduced by Pope Gregory XIII in October 1582, and into
' Britain and its then colonies in September 1752) two
' correction factors are added to make the cycle more
' accurate.
'



Dim golden As Integer
Dim solar As Integer
Dim lunar As Integer
Dim pfm As Integer
Dim dom As Integer
Dim tmp As Integer
Dim easter As Integer

' the Golden number */
golden = (iYear Mod 19) + 1

If iYear <= 1752 Then
    ' JULIAN CALENDAR */
    ' the "Dominical number" - finding a Sunday */
    dom = (iYear + (iYear \ 4) + 5) Mod 7
    If dom < 0 Then dom = dom + 7

    ' uncorrected date of the Paschal full moon */
    pfm = (3 - (11 * golden) - 7) Mod 30
    If (pfm < 0) Then pfm = pfm + 30
Else
    ' GREGORIAN CALENDAR */
    ' the "Dominical number" - finding a Sunday */
    dom = (iYear + (iYear \ 4) - (iYear \ 100) + (iYear \ 400)) Mod 7
    If (dom < 0) Then dom = dom + 7

    ' the solar and lunar corrections */
    solar = (iYear - 1600) \ 100 - (iYear - 1600) / 400
    lunar = (((iYear - 1400) \ 100) * 8) \ 25

    ' uncorrected date of the Paschal full moon */
    pfm = (3 - (11 * golden) + solar - lunar) Mod 30
    If (pfm < 0) Then pfm = pfm + 30
End If

' corrected date of the Paschal full moon - days after 21st March */
If ((pfm = 29) Or (pfm = 28 And golden > 11)) Then pfm = pfm - 1

tmp = (4 - pfm - dom) Mod 7
If (tmp < 0) Then tmp = tmp + 7

' Easter as the number of days after 21st March */
easter = pfm + tmp + 1

If (easter < 11) Then
    EasterOf = DateSerial(iYear, 3, easter + 21)
Else
    EasterOf = DateSerial(iYear, 4, easter - 10)
End If

End Function