Calendar History & More
An old saying about the birth day of a child goes:
"Monday's child is fair of face, Tuesday's child is full of grace, Wednesday's child is full of woe, Thursday's child has far to go, Friday's child is loving and giving, Saturday's child works hard for a living, but the child who is born on a Sunday is bonny, blithe, good and happy."
If might be interesting to check to see if any of these traits fits yourself or any other member of your family by finding out what day you were actually born on. The program that follows allows the user to enter a date in time and the computer will calculate and tell you what day of the week that your date in time actually fell on. This can be a birthday, or of course any date that you wish to check on. You can pick any date now, in the future, or in the past....with a few exceptions.
Any date now or in future can be chosen, but there is a first date restriction for the past. The paragraphs that follow will tell what that first date restriction is, and will give you a brief history of the calendar which will in turn explain why the first date restriction is what it is.
This formula will only work on dates that are after the 13th of September 1752. Why you may ask?
It all has to do with the calendar we currently use. We (the Western world) use the Gregorian calendar. This has been in use since the 15th of October 1582 - but not by everyone. The calendar in use prior to that was the Julian calendar and that was in use by "Westerner's" since the birth of Rome. The Julian calendar was basically the same, a 365 day calendar with leap years, but it had a small discrepancy that put the calendar off by about 7 days per 1000 years, so by 1582 when Pope Gregory XIII decided to remedy the situation there was a 10 day discrepancy he had to fix.
A Jesuit astronomer named Christopher Clavius was actually responsible for designing the new Gregorian calendar, although as you can see the Pope gets the credit in name. Without going into all the technical problems with Julian calendar, the basic solution Clavius devised is based around leap years.
As you may or may not know there is a leap year every four years, or there was in the Julian calendar. The only big change Clavius made to the new calendar was that all years were not destined to be leap years. Yes, every four years is still a leap except for those actual century years which are not multiples of 400. This was the simple solution to make the calendar as accurate as possible.
Most people probably don't know that every fourth year is not a leap year. That's because there are very few years that aren't. Yes, the year 2000 is a leap year, but the year 2100 isn't. The year 1600 was a leap year, but the years 1700, 1800, and 1900 were not. A further example - the year 1896 was a leap year, 1900 wasn't but 1904 was, and so on. This is the Gregorian calendar.
The year 1600 was and the years 2000 and for that matter 2400 and 2800 will be leap years because they are multiples of 400. Get it?
This brings us to calendar reform. When Pope Gregory made the new calendar the law they had to lose some days. Thursday the 4th of October 1582 was the last day of the Julian calendar. The day after the 4th was deemed to now be Friday, the 15th of October, thus losing the necessary days to make the calendar accurate. Technically the Zeller formula works back to the the 15th of October 1582 (if programmed to do so), but there were further problems to come...
This new calendar was made law by the Pope and took immediate effect in all Roman Catholic countries of the time. But the protestants were hesitant, especially - you guessed it - Great Britain. The new calendar was not made 'law' in Great Britain for quite some time... And I bet you can now guess when that first date restriction I gave up near the top came from? That's right, the 14th of September 1752 was the date that Great Britain and those colonies of hers across the Atlantic finally gave in and made the Gregorian calendar law. By that time they had to lose 11 days. This happened by making the day after the 2nd of September 1752, the 14th of September 1752. Can you imagine the outcry of the time? People were not too happy to find out that they were losing 11 days of their life!!
That's why the formula is not valid before 14 September 1752. Like I said earlier the formula would work back to Pope Gregory's time; if you were trying to look up a date in history of say Spain or Italy where the calendar was valid. Any date you tried to look up in British or American history prior to 14 September 1752 just wouldn't be correct. And since the author has close associations with both countries he has put in effect the date Britain and her colonies made the Gregorian calendar law.
References: Encyclopedia Britannica
Sept. 14, 2010