Converting Dates between Gregorian to Afghani Calendar

Hello,

I need your help in creating a calendar that converts the dates from Gregorian Calendar to Afghani Calendar. Afghani Calendar is solar calendar which mean it has 365 days. It is not Lunar Calendar. So year 2006 = 1385 afghani calendar. So this mean that G= A + 621 and A= G- 621.

The problem I have is converting the months and days. The new year for Afghani Calendar is march 20 or 21 (depends on which day is the first day of spring). So the new year 1/1/2006 is 3/20/1385.

I would like to create a excel file that does this conversion and as well show the month and days graphically.

On Tue, 25 Jul 2006 01:27:45 -0400, kjaan wrote in
microsoft.public.excel:

>I need your help in creating a calendar that converts the dates from
>Gregorian Calendar to Afghani Calendar. Afghani Calendar is solar
>calendar which mean it has 365 days. It is not Lunar Calendar. So year
>2006 = 1385 afghani calendar. So this mean that G= A + 621 and A= G-
>621.
>
>The problem I have is converting the months and days. The new year for
>Afghani Calendar is march 20 or 21 (depends on which day is the first
>day of spring). So the new year 1/1/2006 is 3/20/1385.

That doesn't look right; shouldn't that be "1/1/1385 is 3/20/2006"?

>I would like to create a excel file that does this conversion and as
>well show the month and days graphically.

What about months? How long are they and how many are there? And some
years must have a number of days other than 365 depending on the true
vernal equinox in the adjacent years, no?

In principle, I think one has to compute an "absolute" day number, often
called the Julian day number, from the Gregorian calendar. This is often
based on the date 1-Jan-4713 BC. Then with some MOD and integer division
one should get the Afghani date.

However, the true date of the vernal equinox, which can be March 19, 20,
21, is probably a non-trivial algorithm; "Astronomical Algorithms" (Jean
Meeus) might help. There are several web sites which show a JavaScript
implementations; here's one:
<http://www.stellafane.com/misc/equinox.html>. Good luck.

--
Michael Bednarek http://mbednarek.com/ "POST NO BILLS"

anyone out there to help me on this problem. Thanks

On Fri, 28 Jul 2006 02:31:06 -0400, kjaan wrote in
microsoft.public.excel:

>anyone out there to help me on this problem. Thanks

This is a non-trivial problem where not many people are sufficiently
familiar with either one of the calendars involved; most people would be
hard pressed to come up with an algorithm to convert in both directions
between Gregorian dates and Julian days; even fewer, myself included,
have any grasp of the Persian calendar.

You are probably much better equipped to tackle this problem yourself,
either by writing VBA code or even with researching existing approaches.
A web search for "persian calendar conversion" showed many promising
results. Maybe one of them has their algorithm published.

Good luck.

--
Michael Bednarek http://mbednarek.com/ "POST NO BILLS"