Skip to main content

Calculating easter sunday in different ways


Once a long time ago I found an interesting document on the inter web, describing different calendar systems.

From that I made a php-class for my website that can calculate easter sunday in the gregorian calendar. Then it is easy to calculate the rest of the danish holidays as they are offset according to easter sunday (except of course those that have a fixed date).

I translated that class in to x++.

You can find it here:

https://onedrive.live.com/redir?resid=9B63D38F981FFD1B!39710&authkey=!ABv0yYPULV3ReIE&ithint=file%2cxpo

Today I got talking with a colleague about calculating easter sunday so he mentioned that he had also made a version of the calculation:

http://stackoverflow.com/questions/11048524/how-to-calculate-easter-sunday-in-x

So of course - being a bit nerdy - we just *had* to check if the routines arrived at the same result. So we came up with:


static void EasterTest(Args _args)
{
    Yr x;
    date easter(Yr yr) // Påskedag / påske søndag
    {
         int g,c,h,i,j,l;
        int easterday, eastermonth;
        g = yr mod 19;
        // Gregorian Calendar
        c = real2int(rounddown(yr / 100,1));
        h = (c - roundDown(c/4,1)-rounddown(((8*c)+13)/25,1)+(19*g)+15) mod 30;
        i = h - rounddown(h/28,1)*(1- rounddown(29 / (h+1),1) * rounddown((21-g) / 11,1));
        j = (yr + (rounddown(yr/4,1))+i+2 - c + (rounddown(c/4,1))) mod 7;
        l = i - j;
         easterday = 3+rounddown((l+40)/44,1);
        return mkdate(l+28-31*rounddown(easterday / 4,1), easterday, yr);
    }
     date dateOfEaster(Yr y)
    {
         int a = y mod 19;
        int b = y div 100;
        int c = y mod 100;
        int d = b div 4;
        int e = b mod 4;
        int f = (b+8) div 25;
        int g = (b-f+1) div 3;
        int h = (19*a+b-d-g+15) mod 30;
        int i = c div 4;
        int k = c mod 4;
        int l = (32+2*e+2*i-h-k) mod 7;
        int m = (a+11*h+22*l) div 451;
        int n = (h+l-7*m+114) div 31;
        int p = (h+l-7*m+114) mod 31;
        return mkdate(p+1,n,y);
    }
     for (x = 1900; x <= 2154; x++)
        if (dateOfEaster(x) != easter(x))
            info(strFmt('E1=%1 E2=%2', dateOfEaster(x), easter(x)));
}

And the routines calculated the same dates for easter sunday.

We stopped ourselves when discussing if we should implement a tick-couting-measurement to see if my colleagues routine was faster than mine. :-)

But I think mine is slower as it uses several function calls and not pure arithmetic.

Labels

Labels:

Comments

Post a Comment

Popular posts from this blog

Suppressing the infolog

Supressing the infolog is often useful in D365FO when augmenting code. When augmenting code using COC (Chain Of Command), you can have new code run either before or after the code you are augmenting. This means that any infolog-messages that the standard application code does, will be shown to the user, even if your augmentation supports a scenario where there must be no infolog-messages. How do you avoid the standard application infolog-messages ? To the rescue comes temporary supression of the infolog. The suppression consists of: 1) Saving the current infologLevel 2) Setting the infologLevel to SysInfologLevel::None 3) Run your code 4) Restoring the saved infologLevel to the infolog For example a table could have a validatewrite-method that validates that you are only allowed to use 3 out of 6 options in an enum-field, and you need to allow for a fourth one. Table a - validateWrite method: boolean validateWrite() {     Switch (this.enumField)     {     ...
Post a Comment
Read more

Dynamics AX 2012 ValidTimeState tables and form changing view from current to all

Valid Time State tables are new i AX 2012 a gives the developer the possibility to easily create tables that hold e.g. current setup data for various purposes, and at the same time keeping a "history" of the changes of the data in the table. For more reading: http://msdn.microsoft.com/en-us/library/gg861781.aspx I was tasked with doing a setup table with rates for calculating Vendor Bonus and I chose to base this a valid time state table. The customer asked for a button on the form, where you maintain the vendor bonus calculation setup data, so you could toggle viewing "Current setup" or "All setup" records (changing the view from actual to all records and vice versa in the form). I found that you can not change the ValidTimeStateAutoQuery property on the form data source in a form at run-time. It simply does not change anything, so I came up with the following solution: A boolean class member in the classdeclation method of the form: boolean ...
Post a Comment
Read more

Subtle but important difference between _ds.executeQuery() and ds.Research()

This is actually an old entry. Been tumbling with a problem for the last few days. A form in our Dynamics AX module for Preventive Maintenance Control was not behaving. The form has "explicit" filter fields that the user can see without having to activate the form filter (CTRL+F3), for setting up filters most commonly used in an easy way. And this is working ok. However at this customer site, the form has been adjusted so that the user can have the form refreshed automatically periodically, and when the users at the customer site were making use of the "explicit" filter combined with the AX's normal filtering (CTRL+F3), the form simply threw away the normal form filtering. I discovered a subtle but very important difference between writing _ds.executeQuery(); (which was the way our code was doing it) and _ds.Research(); The difference is that _ds.Research() will retain the filter ranges in the forms query as they are right now. _ds.executeQuery() will NOT. It ...
Post a Comment
Read more