This project started when I wanted to have easy access to the calendar while I'm not home. Before, I would be like any other normal person and take photos of the one we have at home. I also wanted to be able to look back and see what days the Holy days landed on in previous years.
I thought, why not make a program that can create the calendar for any year you wanted? Surely it wouldn't be that difficult, right? All I need to do is figure out the rules and with my computer knowledge, write up a script to follow those rules in order to make a calendar.
First thing I started with was Pascha. How do you figure out where it lands on a given year? Well, with some research, I've found that it lands on the first Sunday after the first full moon, after the vernal equinox (march 21st). Of course this is going by the old calendar (the Julian or Byzantine calendar).
This ends up making a 19 year cycle for the placement of Pascha.
There are a handful of Holy days that end up following/preceding the placement of Pascha as well as placements and lengths of certain lents. After that, the rest of the Holy days are on the same day each year, simple enough.
Another thing I had to account for is the drift between the calendars. When the Gregorian calender (the calender most of the world uses today) was intoduced back in October 1582, they skipped forward 10 days. They also skip 3 leap years every 400 years. Which is why they are 13 days apart as of today. In the code, I've put in a formula to check what the drift is for any given year and adjust everything to be accurate. For example, we celebrate Christmas on January 7th (Dec 25th on the old calendar), but starting after the year 2100, it will move to January 8th on the Gregorian calendar.
If you input a date before 1582, obviously the Gregorian calendar didn't exist then, I just had the program extend the Gregorian calendar backwards as if it did. This is also known as a Proleptic Gregorian Calendar. Not to worry, this doesn't make it innacurate, as we are still going by the old calendar anyways. Even if it did, it would only affect the past, not the future.
Another thing is, what about B.C. Years? For now I haven't figured out how leap years in the Gregorian calendar work before that, I don't think there even is a right answer since it didn't exist then. Also it wouldn't even matter since that was a time before Jesus's Birth.
For now, no. But, I am working on getting this to be as accurate as I can. Some people may say that since I did research from sources outside our denomination/church, this info should not be trusted. I agree, but since I am not proficient enough in church slavonic in order to fully understand exactly what it says, this is my best alternative. I am however doing my best to cross reference everything with the current calendar and previous calendars that are availible to me.
As of right now, to the best of my knowledge, all of the Holy days & lents are matching up with the calendars from other people. The only thing is a good handful of days that say what kind of food we can eat are not correct. I've tried my best to be more safe than sorry, so that if there is a day we can have oil, my calendar should go down the chain, saying no oil instead of meat or fish.
There can still be errors in this calendar, and I do not feel safe recommending that people trust it yet. At some point, I may change that.