The Julian Calendar is the Roman calendar begun in 45 B.C. , named for Julius Caesar who initiated it. It was used by the Roman Empire and the Holy Roman Empire until 1582, when Roman Catholic countries replaced it with the more accurate Gregorian Calendar. Other countries switched over later: English countries in 1751, and some Greek Orthodox countries as late as 1940.
It is our modern calendar used virtually worldwide as a civil calendar. It differs only very slightly from the Julian Calendar. The Julian calendar inserts a leap day every four years to keep it aligned with the solar year, which is about 365 1/4 days long. The Gregorian recognizes that the year is really about 365.242 days in length, and makes the correction of skipping the leap day in 3 out of 4 centuries (The year 2000 will be a leap year, but 1700, 1800, and 1900 were not).
The Julian and Gregorian calendars agreed in the fourth century A.D. Thereafter, they differ by about one more day each century. In the 1500's and 1600's they differed by 10 days, in the 1700's by 11 days, and so on.
The English version of the Julian Calendar was called the "Old Style" Calendar after they adopted the Gregorian, which was also called New Style. The only difference between the English Old Style and the Julian was that the year began on March 25. That is, the day after March 24, 1711 was March 25, 1712. Because of this, I have implemented both the Julian and the Old Style calendars in my conversion program.
In the 1600's and first half of the 1700's nearly all of Europe used the Gregorian calendar, but the English continued to use their Old Style Calendar. Thus, dates before March 25 were in one year for the English but in the next year for others. To avoid confusion, it became the standard notation to write both years. Thus, the date "Feb 24, 1731/32" means it was near the end of the year 1731 in England, but in the beginning of 1732 on the Gregorian calendar. Notice that it only makes sense to use that notation for dates on or before March 24th because from March 25th on the years were the same.
When George Washington was born the calendar on the wall in the English Colonies read February 11, 1731 (or 1731/32). In other countries still using the Julian calendar, it was February 11, 1732 because their year began on Jan 1, rather than March 25. In most European countries such as Italy, Spain and France, which used the modern Gregorian calendar, the same day was called February 22, 1732. After the Colonies adopted the Gregorian calendar on January 1, 1752, the date of Washington's birth has been considered to be February 22, 1732.
To make astronomical calculations easy, Julian Scaliger introduced the idea of numbering all the days sequentially. Astronomers still use this convention because it is a great way to identify a day precisely. Thus, days numbered this way are called "Julian Days," named for him, not for Julius Caesar (as is the Julian Calendar!). He began numbering from Jan 1, 4713 B.C., in order that all historical days would have a positive number.
The Mayan calendar has a continuously repeating cylce of twenty days, each of which is named. Mayan Priests said that the names represented days in man's life, such as birth and death. Each is explained in detail on another page.
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