Calendar woes

The first bit of Calendar nonsense I encountered today was some spam that a family member felt compelled to forward. The message was:

Money bags

This year, July has 5 Fridays, 5 Saturdays and 5 Sundays. This happens once every 823 years. This is called money bags. So, forward this to your friends and money will arrive within 4 days. Based on Chinese Feng Shui. The one who does not forward.....will be without money.

Kind of interesting - read on!!!

This year we're going to experience four unusual dates.

1/1/11, 1/11/11, 11/1/11, 11/11/11 and that's not all...

Take the last two digits of the year in which you were born - now add the age you will be this year,

The results will be 111 for everyone in whole world. This is the year of the Money!!!

The proverb goes that if you send this to eight good friends, money will appear in next four days as it is explained in Chinese Feng Shui.

Those who don't continue the chain won't receive.

Its a mystery, but it’s worth a try. Good luck

Okay, so we are now well into August so why am I getting this crap touting how special July was? Well I have given up trying to explain to certain relatives that any mail with the phrase "send to everyone you know" is worthless garbage, but then again I'm enough of a loser to actually read through some of this tripe so I guess I can't complain too much. The first claim is about how special the so called "Money Bags" month is and that it only occurs every 823 years. This immediately strikes me as being wrong. A year is usually 365 days and 365 mod 7 is 1. So if we ignored leap years, then the first of July would return to the same day of week every 7 years. I was too lazy to do the math to see when this would occur and factor in the leap years, that is what computers are good for:

$ gseq 2011 2025 | xargs -I'{}' cal 7 '{}' | grep -B2 -A5 '1  2$' 
     July 2011
Su Mo Tu We Th Fr Sa
                1  2
 3  4  5  6  7  8  9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
--
     July 2016
Su Mo Tu We Th Fr Sa
                1  2
 3  4  5  6  7  8  9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
--
     July 2022
Su Mo Tu We Th Fr Sa
                1  2
 3  4  5  6  7  8  9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31

So clearly the July "Money Bags" month is nothing special. Hopefully posting it on the internet and mocking the message will also bring money my way in 4 days via the awesome power of Chinese scented bullshit. Their next claim is a rigged math test that is supposed to be 111 for everyone in the world. Unfortunately, they seem to have forgotten that a few people have been born after the year 1999, and for those individuals the result will be significantly less than 111. Also, according to wikipedia there are a few people still alive that were born in the 1890s and they will get a number considerably higher than 111.

Well that's enough criticism of the spam email. The second bit calendar fun was from the reference site I used for the end of the world post. It has a number of errors in the description of common mistakes made by those predicting the end of the world. The description provided is:

An untold number of people have tried to predict the Lord's return by using elaborate time tables. Most date setters do not realize mankind has not kept an unwavering record of time. Anyone wanting to chart for example 100 BC to 2000 AD would have contend with the fact 46 BC was 445 days long, there was no year 0 BC, and in 1582 we switched from Julian Years (360 days) to Gregorian (365 days). Because most prognosticators are not aware of all these errors, from the get go their math is already off by several years.

The basic idea is correct, that is there have been many calendars over time and the nuances of those calendars makes it very difficult if not impossible to determine exactly when recorded events happened. So it is true that 46 BC was 445 days long because of accumulated errors in the Roman calendar. However, it fails to mention that 45 BC was the first year that the Julian calendar started getting used. It is also true that there is no 0 year in either the Julian or Gregorian calendars and that some Catholic countries adopted the Gregorian calendar in 1582, but adoption was a long process that took hundreds of years. For example, Greece did not adopt the Gregorian calendar until 1923.

This brings us to the most glaring mistake, that is the claim that the Julian year was 360 days. The Julian calendar has 365 days and calls for a leap year every 4 years making the average length 365.25 days. In fact, the primary change with the Gregorian calendar is to fix some of the long term drift that occurs because the actual number of days in a solar year is about 365.25 days - 11 minutes. Do the math, 24 hours / 11 minutes is approximately 131. That means that after 131 years the Julian calendar will be off by a full day. After 393 years the calendar would be off by 3 days. In the Gregorian calendar the rules for leap years were changed to be years divisible by 4 unless the year is divisible by 100, but if the year is divisible by 400 it is still a leap year. This correction is still not exact, but it does a better job than the Julian calendar. I'm just guessing, but maybe they were thinking of the Egyptian calendar that did have 360 days.

It should be pointed out that these errors don't change their premise. If anything their position is reenforced as the there are many more complexities than they indicated. History is messy, and this includes the history of how we measure and record the time.