How Do You Convert Between Julian and Egyptian Calendars?

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In summary, the conversation discusses the topic of calendar conversion theory and the availability of information and equations on the subject. It is mentioned that calendars are not just a set of algorithms and there are various factors such as historical, political, religious, and astronomical aspects involved. The book "Standard C Date/Time Library" by Lance Latham is recommended as a resource for conversions between 40 calendars with supporting C code. However, there is a caveat that there are conflicting resources and potential unreliable sources on the internet. The conversation also delves into the complexities of converting between ancient calendars such as Babylonian, Julian, and Egyptian calendars and the importance of defining initial assumptions. It is recommended to do thorough research and reading on the subject before attempting conversions.
  • #1
lewis198
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Conversion of calendars

Hey guys do you know where I could get info on calendar conversion theory? Including all the equations?
 
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  • #2
It isn't just a set of algorithms. What exactly are you interested in doing?
Do you understand that, for example, some calendars underwent reformation at different times in different countries - the Julian - Gregorian is one.

A book (minus some problems about year counting with regard to the Chinese calendar) has a discussion on 40 calendars and conversions between all of them with supporting C code:
Latham, Lance, 1995 'Standard C Date/Time Library: Programming the World's Calendars and Clocks '

Calendars are more about history, politics, religion and early astronomy
than anything else.

All calendric conversions work this basic way:
Convert the date in calendar A to JD (Julian days)
Convert JD to calendar B date.

Not all conversions are valid all the time. My experience is that there are good resources for some conversions, and conflicting resources for others.
 
  • #3
Can you be more specific? Julian calendar vs Gregorian calendar? Mayan calendar vs "modern" calendars? This could quickly get very tricky since conversion from ancient calendars typically involves archaeological dating controversies as well as astronometry. (E.g. controversies abound in Minoan and Egyptian chronologies.)

If you are primarily interested in Western calendars, some books on the theory of algorithms describe conversion algorithms.

For some interesting mathematics, you might look into Coll charts for truly relativistic satellite navigation systems (see the website in my sig and use the search tool). Current proposals for next generation satellite navigation systems really get at the heart of what we mean by timekeeping in a very interesting way, in IMO constitute a true revolution in intellectual history. A sweeping statement, I know, but check it out!

Sadly, I feel that I must add a caveat: calendar systems have always been one of those areas that attract an unusual number of cranks. Ditto archaeological controversies. So on the web you can find quite a few calendar cranks, so be careful that your sources are reliable.
 
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  • #4
Thanks for your reply, I was interested in conversions between Babylonian, Julian and Egyptian calendars. Do you know if formulas exist that provides just that?
 
  • #5
Thanks for your reply, I was interested in conversions between Babylonian, Julian and Egyptian calendars. Do you know if formulas exist that provides just that?
 
  • #6
Yes, Latham's book explains those. And all his assumptions about how his versions work. But like I mentioned, it is not a one-to-one deal. There are different starting points for the Middle Egyptian calendar, for example. It supposedly works on a "heliacal cycle" of ~1460 years, and is also based in part on the flooding of the Nile. Therefore, a lot of dates you can come up with from other calendars may not make sense. You use different formulas depending on which starting point you choose, for example.

This may sound odd, but calendars are 'consumer items', perfect only as defined by the person who understands the one being used. If this is for even slightly serious work you should consider doing a lot of reading.

Just like in Math, as long as you define your initial assumptions and then say date y (in calendar system A)= date x (in calendar system B) you are okay.
Calendars can be an endless source of debate IMO.

Start with wikipedia, which may have some minor errors:

http://en.wikipedia.org/wiki/Julian_calendar

http://en.wikipedia.org/wiki/Egyptian_calendar
Some of the ideas here seem to disagree with some the assumptions Latham uses (Sothis rising cyle thing). I am not saying who is right or wrong because I don't know.
 
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  • #7
lewis198 said:
Hey guys do you know where I could get info on calendar conversion theory? Including all the equations?
Please don't post your question multiple times.
 
  • #8
sorry about that.
 
  • #9
I have looked up the julian day number, but many websites simply use the example of the gregorian to julian or julin day number examples. Do you guys know any general algebra for one calendar date to another?

Specifically, I would be converting between Julian and Egyptian calendars.
 

FAQ: How Do You Convert Between Julian and Egyptian Calendars?

What is calendar conversion theory?

Calendar conversion theory is a scientific concept that proposes the idea of converting calendars from one system to another. This theory suggests that with proper mathematical calculations and adjustments, different calendars can be synchronized and converted into each other.

Why is calendar conversion theory important?

Calendar conversion theory is important because it helps us understand and study the different ways in which different cultures and civilizations have measured time. It also allows for better communication and synchronization between calendars, which can be beneficial for international trade and collaboration.

What evidence supports calendar conversion theory?

There is evidence of calendar conversion being practiced in ancient civilizations, such as the Mayans and Egyptians. Additionally, modern day astronomers use calendar conversion theory to accurately predict and record astronomical events, further supporting the validity of this theory.

What are the challenges with calendar conversion?

One of the main challenges with calendar conversion is the difficulty in accurately converting dates and times from one calendar system to another. This is due to the differences in the length of a year, month, and day in different calendars. Additionally, cultural and historical meanings attached to certain dates may not always align when converting calendars.

What are the potential implications of calendar conversion theory?

If calendar conversion theory is proven to be accurate, it could have significant implications for international communication, trade, and cultural understanding. It could also lead to a better understanding of historical events and the alignment of different calendars could improve the accuracy of astronomical predictions and studies.

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