A proposed calendar change to fix date keeping

This article is partly inspired by an article I read and partly by a question from a friend in response to a comment I made about the calendar. The friend said, “How was the calendar discovered?” This question implies that the calendar pre-existed like fossil seashells waiting to be found. This is only partially true. Important parts of the calendar were discovered by measurement; others were invented as conveniences to make the calendar easier to use.

Tens of thousands of years ago, people were as intelligent as we are today. They had observed the sky and seasons and arrived at several measurements. On the day of the winter solstice, the sun is lower in the sky at noon than on any other day. This is easy to determine by observing the length of the shadow of a vertical pole. When the shadow is longest at noon, the daylight period is the shortest, and the sun is lowest in the sky at noon.

Counting the number of days from one solstice to the next yields 365. For convenience, the year is divided into two types of intervals. Based on the approximate time it takes the moon to go through its phases, the interval ‘month’ is about 30 days long and the interval ‘week’ is seven days long. The Hebrew Bible explains the seven days, but many archeological sites show the seven-day week to be in use before the Bible was written. One idea is that the lunar month can be divided into four parts of seven each. Another idea is that seven round objects such as tent poles can be tied into a stable configuration with six poles surrounding the seventh.

If you tried to predict the solstice over the next few years, after four years you would be off by one day. The length of time for the earth to rotate once does not divide evenly into the length of time for the earth to revolve once around the sun. It takes about 365 and one-quarter days for the revolution so every four years you must adjust your calendar.

The Julian Calendar, established in 45 BCE, had 11 fixed months of 30 or 31 days, and one month, Februarius, which varied. For three years, it would be 28 days and then for one year, it would be 29 days. Although this seems very similar to our calendar, it differs in that every four years, Februarius would have 29 days.

Because the length of the year is actually about 11 minutes than 365.25 days, over centuries, the solstice would drift away from the predicted date. By the 16th century, it was off by about 10 days.

Pope Gregory XIII decreed that Thursday, October 4, 1582 was followed by Friday, October 15, 1582. Gregory also instituted a small change in the rule for determining leap years. The old rule was any year evenly divisible by four was a leap year. The new rule added two clauses. The rule is now: if a year is divisible by four, it is a leap year, unless it is divisible by 100 when it is not a leap year, unless it is divisible by 400 in which case it is a leap year.

Examples:

2012 is divisible by four and will be a leap year

1900 was divisible by four and by 100 and was not a leap year

2000 was divisible by four, 100 and 400, and was a leap year

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On December 30, 2011, the Sioux Falls Argus Leader, reprinted an article from USA TODAY entitled, “Proposal would keep calendar same each year.” 

Richard Henry, a professor of applied physics at Johns Hopkins, and, Steve Hanke, a Johns Hopkins economics professor, propose a calendar that would have four months with 31 days: March, June, September, and December. The other months would have 30 days including February. This accounts for 364 days, which is evenly divisible by seven. You could have a calendar carved into a wall and never change it since your birthday, for example, would always fall on the same day of the week. Christmas would always be on a Sunday; July 4th would always be a Wednesday; Labor Day would always be September 5th. Halloween would move to October 30th, since there would be no October 31st.

“But, wait,” I hear you say, “364 is less than the time for a revolution by about one and one-quarter days. What about the drifting of the solstice?”

Henry and Hanke propose to have a leap week of about five days every five or six years to adjust the proposed calendar and keep it in harmony with the seasons and January 1st always being a Monday.

One of the major objections to this proposed calendar comes from religious groups who believe it is ordained that every week have seven days.

Another problem arises for people whose birthdays previously fell on January, May, August or October 31st. Furthermore, how would you treat the birthdays of those born during the leap week?

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On a related note, the island nation of Independent Samoa traveled into the future on December 29, 2011, by skipping over December 30, 2011 and jumping officially to December 31, 2011.

Samoa previously lagged behind Los Angeles, CA by two hours and behind Sydney, Australia by 21 hours. By jumping one day into the future, Samoa is now three hours ahead of Sydney, one hour ahead of Wellington, New Zealand, and 22 hours ahead of Los Angeles. A time alignment with Australia and New Zealand makes sense to Samoa because the majority of Samoa’s business is with them rather than with California.

An interesting religious question arises for Jews, however. Since there was no Friday, December 30, 2011, when is the start of Shabbat, a 49-hour period of refraining from work? Shabbat is supposed to start a few minutes before sunset on Friday, but there was no Friday! You can read more here.

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