On Fri, 27 Mar 2009 09:14:58 -0400, "Bernie Deitrick" <deitbe @ consumer dot

org wrote:

Bernie,

I'm not smart enough to follow what the function is doing. I noticed that in

the

VB Editor it doesn't seem to mater if \ of / is used as a division

indicator. I changed it in one place and the code still ran properly. I

thought that possible "SynchWithMoon" might show some relationship to the date

of the full moon before Easter. If it does, I can't discern it.

As a side note, Easter can fall on any Sunday from March 22 to April 25.

Thanks for your help. I can still use your equations to calculate full moons

in relation to the known date of any one full moon.

Chuck

I don't think that the formula calculates anything about the full moon - it is most likely that the

pattern of Easter Sundays fit some other discernable pattern (which I certainly cannot figure out).

But setting one full moon should be able to predict full moons many years into the future or past -

with a slight modification, the code correctly return the moon dates in 1901.

From the same contest that gave that function:

=TRUNC(DATE(J,7,-CODE(MID("NYdQ\JT_LWbOZeR]KU`",MOD(J,19)+1,1)))/7)*7+8

where J is the year...

But this VBA Function may give you a better idea of how the math is done:

Function EASTER(Yr As Integer) As Long

Dim Century As Integer

Dim Sunday As Integer

Dim Epact As Integer

Dim Golden As Integer

Dim LeapDayCorrection As Integer

Dim SynchWithMoon As Integer

Dim N As Integer

Golden = (Yr Mod 19) + 1

Century = Yr \ 100 + 1

LeapDayCorrection = 3 * Century \ 4 - 12

SynchWithMoon = (8 * Century + 5) \ 25 - 5

Sunday = 5 * Yr \ 4 - LeapDayCorrection - 10

Epact = (11 * Golden + 20 + SynchWithMoon - LeapDayCorrection) Mod 30

If Epact < 0 Then Epact = Epact + 30

If (Epact = 25 And Golden 11) Or Epact = 24 Then Epact = Epact + 1

N = 44 - Epact

If N < 21 Then N = N + 30

N = N + 7 - ((Sunday + N) Mod 7)

EASTER = DateSerial(Yr, 3, N)

End Function

HTH,

Bernie

MS Excel MVP

"Chuck" wrote in message ...

On Thu, 26 Mar 2009 08:50:59 -0400, "Bernie Deitrick" <deitbe @ consumer dot

org wrote:

Burnie,

I have an equation that accepts an input of a year (2009) and from this single

input it calculates the Month and Day for Easter of that year.

=FLOOR("5/"&DAY(MINUTE(YEAR({year})/38)/2+56)&"/"&YEAR({year}),7)-34

It is not my equation. It is something I found on the internet a fair number

of years ago. Since Easter is the first Sunday after the first full moon on or

after the Vernal Equinox (March 21), the equation some how calculates the date

for at least one full moon. I've tried to 'pull out' that full moon date. But

I'm just not smart enough.. If the date of that full moon can be had from a

single equation, that date can be the reference date to calculate full moons

for the rest of the year using you subroutine.

--

Chuck

Chuck,

There is a page at the Naval Observatory:

http://aa.usno.navy.mil/data/docs/MoonPhase.php#y2009

I just picked two from early this year, and adjusted UTC to EST.

HTH,

Bernie

MS Excel MVP