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Calendar for Any Year from 1AD to 9999AD
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"Our units of temporal measurement, from seconds on up to months, are so complicated, asymmetrical and disjunctive so as to make coherent mental reckoning in time all but impossible. Indeed, had some tyrannical god contrived to enslave our minds to time, to make it all but impossible for us to escape subjection to sodden routines and unpleasant surprises, he could hardly have done better than handing down our present system. It is like a set of trapezoidal building blocks, with no vertical or horizontal surfaces, like a language in which the simplest thought demands ornate constructions, useless particles and lengthy circumlocutions. Unlike the more successful patterns of language and science, which enable us to face experience boldly or at least level-headedly, our system of temporal calculation silently and persistently encourages our terror of time.

"It is as though architects had to measure length in feet, width in meters and height in ells; as though basic instruction manuals demanded a knowledge of five different languages. It is no wonder then that we often look into our own immediate past or future, last Tuesday or a week from Sunday, with feelings of helpless confusion."
Robert Grudin, `Time and the Art of Living'

The Julian Calendar

The Julian Calendar was introduced by Julius Caesar in 46 BC, but in those days the year number was the number of years since the founding of Rome (753 BC in the modern calendar). The original Julian calendar had 12 months starting with March of alternately 31 and 30 days with February (the last month) having 29 days - giving a total of 365 days. In a leap year (every forth year) the months have alternately 31 and 30 days giving a total of 366 days. Thus, in non-leap years the last month February would have 29 days is place of its usual 30. The name of the fifth month (Quintilis) was changed to Iulius (July) in 44 BC and Sextilis (Sixth month) as Augustus (August) in 8 BC.

Month Days in leap year Days in non-leap year
March 3131
April 3030
May 3131
June 3030
Quintilis / Iulius / July 3131
Sextillis 3030
September 3131
October 3030
November 3131
December 3030
January 3131
February 3029
TOTAL 366365

The Augustus Change

Augustus modified the Julian calendar by moving one day from February to August, so that the length of Augustus would not be shorter (and therefore inferior) than the length of Iulius, one day from September to October and one day from November to December. This gives us the scheme of days in each month that we are all familiar with.

Month Days in leap year Days in non-leap year
March 3131
April 3030
May 3131
June 3030
Iulius / July 3131
Sextillis / Augustus / August 3131
September 3030
October 3131
November 3030
December 3131
January 3131
February 2928
TOTAL 366365

The 11 Minute Error

Although the Julian calendar at 365 days per year is fairly accurate, it is in fact 11 minutes and 10 seconds too long. By the mid 1500s it was 17 650 minutes or 11.6 days adrift from astronomical time.

The Gregorian Calendar

The Gregorian calendar - also known as the New Style was introduced by Pope Gregory XIII in 1582 but was not adopted by Great Britain until 1752. It modified the Julian calendar in order to correct the accumulated errors of 11 minutes 10 seconds in each Julian year. 10 days were removed in 1582 in those countries that adopted the Gregorian calendar. Great Britain removed 11 days in September 1752 when it adopted the Gregorian calendar.

The Gregorian Reformation is assumed to have occurred in 1752 on the 3rd of September. By this time, most countries had recognised the reformation (although a few did not recognise it until the early 1900's.) Ten days following that date were eliminated by the reformation, so the calendar for that month is a bit unusual.

When the Gregorian Calendar was adopted the following significant changes occurred:

  • Drop 10 days from October 1582 (11 from September 1752), to realign the Vernal Equinox with March 21st. The Julian Calendar, first adopted by Julius Caesar for the Roman Empire in 45 BC, had an annual error factor of .00636 days. From 45 BC to 1582 AD, the correct day of the Vernal Equinox using the Julian Calendar fell behind by a full ten days.
  • Reduce the number of possible leap years. In the Julian Calendar, a leap year occurred every four years. By reducing the number of leap years, the Gregorian Calendar was able to more closely align the Vernal Equinox over centuries. The change was to make leap years for years ending in "00," but only if the number could be divided evenly by 400. The year 2000 is a leap year (2000/400=5), while the year 1900 was not (1900/400=4.75).
  • Change the first day of the year from March 25th to January 1st. This was the most dramatic change from the Julian to Gregorian Calendar. Traditionally, the new year was determined by the beginning of the four seasons, and through several centuries, the first day of Spring in the Julian Calendar was on or about March 25th.

Double Dating

When the first day of the year changed from March to January in 1752 people began writing dates between January 1st and March 25th both ways, reflecting the "Old Style" (OS) And the "New Style" (NS), which genealogists may find indicated in old records from September 1752 forward. Someone born between 1st January and 25th March in years 1752 and before would indicate the date as 22nd February 1731/2 to indicate that in the Julian calendar they were born in 1731 but in the Gregorian calendar it was 1732. The double dating indicates the situation of a date between January 1st and March 25th. As a genealogist, any date you find in old records before 1752, and between January 1st and March 24th, inclusive, should be expressed as a double date. The authors of the documents did not do it for you in most cases. There may have been some anticipation of the calendar change in the British Empire just before 1752, but in most cases, finding a date written as 22 February 1731/2 is rare. What was written was the Julian date of 22 February 1731. After 1752, the use of double dating was widespread in the old documents. In order to calculate ages when the dates span 1752, use the second number in both cases and assume that pre 1752 years start on the 1st January.

Check and Recheck Dates

In the Julian calendar 24th March 1701 is followed by 25th March 1702! So, someone born on 20th March 1701 and dying on 30th March 1702 is only 10 days old. If these dates are expressed as "double dates" it would be shown as born on 20th March 1701/2 and dying on 30th March 1702. This makes it easier to calculate date intervals.


The name Easter comes from Eastre, an ancient Anglo-Saxon goddess, originally of the dawn. In pagan times an annual spring festival was held in her honour. Some Easter customs have come from this and other pre-Christian spring festivals.


The USA Halloween traditions of trick-or-treating and jack-o-lanterns were brought to America in the 1840s by Irish escaping the Great Potato Famine. On Halloween, Irish peasants begged the rich for food and played practical jokes on those who refused. To avoid being tricked, the rich handed out cookies, candies, and fruit - a practice that turned into the present day trick-or-treating.

Jack-o-lanterns trace back to an old Irish tale about a man named Stingy Jack. Unable to enter Heaven because of his stingy ways and turned away by the Devil, Stingy Jack wandered the world, searching for a resting place. To light his way, Stingy Jack used a burning coal in a hollowed out turnip -- hence the name "jack-o-lantern." The first jack-o-lanterns, in fact, were carved out of turnips. Only when the Irish tradition reached America did turnip carving turn into pumpkin carving.

Witch means wise one. It comes from the Saxon word wica. Witches were thought to be wise enough to tell the future.

Orange and black became Halloween colours because of orange is associated with harvests and black is associated with death.

Halloween is the 8th largest card-sending occasion in the USA. There are over 28 million Halloween cards sent each year!

There are many variations on the history of Halloween, but it's generally believed that Halloween dates back to 700 BC to the Celts, a rural society in northern England, Scotland and Ireland. On November 1, the first day of their new year, the Celts celebrated a festival called Samhain ("sow-in").

Chosen to signify the end of the harvest season and the onset of winter, Samhain was also thought to be a day of the dead. Because it was the end of one year and the start of another, the Celts believed that past and present were closely linked, allowing ancestral spirits to join them.

On the eve of Samhain, October 31, the Celts dressed in costume, lit bonfires, and offered food and drink to masked revellers. Many say the costumes and fires were used to drive away the spirits, and the food given to placate the dead.

October 31 came to be called Halloween when the Christians proclaimed November 1 as All Hallow Day. Unable to stop the pagan ritual of Samhain, the Christians made it a day to celebrate saints who had no day of their own. The night before, or All Hallow Eve, was later shortened to Halloween.

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Last Updated: Monday, 04-Feb-2019
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