Julian Calendar Specification

The Julian name for calendar structure is ambiguous. Technically is applies to the Roman calendar introduced in 45 BC. The name is popularly applied to the Christian Era calendar with New Years on March 25.


Properly speaking the Julian Calendar was introduced by Julius Caesar in 45 BC. This followed 46 BC, a year of correction, which was also the result of Julius’ actions. That said, the calendar went through further revision by Augustus Caesar introduced in 8 BC which is the first year with a calendar shape identical to the modern Julian Calendar. By this measure it should be called the Augustus Calendar. This was not the end of revisions, though, that lead to the current Julian calendar.

Very early in Church history the date for New Years was shifted from the pagan, Roman, definition of January 1, to March 25. This was apparently a reflection of the early church belief that Jesus’ was raised from the dead on Sunday March 25, 31 AD. We discuss this entire topic as part of our Jesus’ Life section.

This change to March 25 was done for religious reasons, but it "stuck" in the governments of various western nations and became the common calendar. When England, and her colonies, eventually switched to the modern Gregorian calendar New Years day was shifted back to the pagan date of January 1.

Having New Years Day fall in the middle of a month brings havoc with many of the calendar conventions that we are used to. Consider that expressions like "Last June" implictly imply the year. But, under the Julian calendar with New Years on March 25, expressions like "March, 1701" are now hard to discipher. March 25 through 31 fell at the start of 1701, while March 1 through 24 fell at the end.

The following is the structure of Julian calendar used from the start of the Christian era until it was supplanted by the Gregorian Calendar.

Number Name Abr. Common Leap
1 March Mar 7 7
2 April Apr 30 30
3 May May 31 31
4 June Jun 30 30
5 July Jul 31 31
6 August Aug 31 31
7 September Sep 30 30
8 October Oct 31 31
9 November Nov 30 30
10 December Dec 31 31
11 January Jan 31 31
12 February Feb 28 29
13 March Mar 24 24
Totals: 365 366


"With this sort of odd mapping of March into two different places in the annual calendar I would suspect that month numbers were almost never used."

The person who wrote this statement is obviously unfamiliar with the recordkeeping of the period prior to September 1752 (that being the time when England and her colonies changed from the Julian to the Gregorian calendar).

In fact, it was common to record dates entirely by means of numbers. Quakers, in particular, entirely avoided the use of the "pagan" names of the months and recorded the dates of births, marriages and deaths, etc. exclusively by numbers.

March was considered the 1st month of the year because the new year (March 25) occurred during March. January and February were, respectively, the 11th and 12th months of the year. September, October, November and December were, quite properly, called the 7th, 8th, 9th and 10th months of the year - and that is exactly the meaning of roots of the names of these months: "sept" (7), "oct" (8), "nov" (9), "dec" (10).

At any rate, historians and genealogists who deal with the colonial period of America - especially in Massachusetts, where the vital records have been extensively preserved - are well aware of this form of recording dates.