Ancient Roman Calendar

Go to google, and type in "Julian calendar+history"--you should get some good information. Iulius Caesar (generally known as Julius Caesar), revised the calendar. I am frankly clueless as to what reforms were necessary, and what the calendar prior to his reforms was like. The Julian calendar has an inherent error, which the later Gregorian calendar corrected. The English-speaking world used the Julian calendar until the mid-eighteenth century. So, for example, George Washington was considered to have been born on February 11th, 1731 (they also considered the new year to begin on March 20th, Lady Day). By the newly adopted Gregorian calendar, his birthday was "moved" to February 22nd, 1732--the cumulative error at that time was 11 days. The Russians continued to use the Julian calendar right up to the time of the Russian and Bolshevik revolutions. Therefore, the Russians called the Russian Revolution the February revolution (but it took place in March of the Gregorian calendar) and the Bolshevik Revolution was known as the October revolution (even though it occured in November according to the Gregorian calendar). Hence, "Red October" was a popular name for ships, factories, public buildings--Krazny Oktyaber (my ability to tranliterate cyrillic to roman letters is not good, don't quote me).

There are aome good sites out there that explain the Roman calendar. But here are some quick facts. The Roman Calendar started with March (and so September was the 7th month, October the 8th, etc.) and February was the last month. This continued until the Gregorian calendar was adopted in the 1500s (so that when a leap day was added to February, it was an extra day at the very end of the year). Also, the Romans didn't use weeks. Each month was split into 3 sections, and dates were based on their relationship to three important days each month, named the Kalends (the first of the month and the source of "calendar"), the Nones (the seventh day in long month, but the fifth in others) and the Ides (the 15th day in long month, but the 13th in others -- remember "beware the Ides of March" in Julius Caesar).

Anyway, a much more detailed explanation is at:
http://home.comcast.net/~rthamper/html/body_calendar.html

After the introduction of the Julian calendar in 45 BCE, there were a few erros in the application of the rule of the leap year, and application practice was remedied in 4CE. It is not known how they erred in determinning leap years, and the exact dates between 45 BCE and 4 CE in the erred calendar are not clear in the "genuine" Julian calendar.