Our calendar year, the Roman calendar and the Julian calendar

What I already knew: In our calendar year, the months January and February were added on later (there used to be 10 months). This is why September, the 9th month has the prefix "Sept" for 7th, and October, the 10th month has the prefix "Oct" for 8th.

I also knew that July was named after Julius Caesar and August was named after Augustus Caesar.

What I learned today: The Roman calendar started out as a lunar calendar with the following 10 months:

• Martius
  
• Aprili
• Maius
  
• Junius
• Quintilis
• Sextilis
• September
• October
  
• November
  
• December
  

The months Ianuarius and Februarius were later added on to the end of the calendar by one of the traditional Kings of Rome. At this time, the year had 355 days. To align the calendar year with the solar year, Mensis Intercalaris, a leap month was added in.

However, there were problems with this Roman calendar, (which I didn't really learn about,) and Julius Caesar introduced the Julian calendar in 46BC, which had 365 days with a leap year every four years. As a result, the year 46BC was 445 days long.

The Romans later renamed Quintilis (originally 5th month), as Iulius (after Julius Caesar) in 44BC and renamed Sextilius (originally the 6th month), as Augustus (after Augustus Caesar) in 8BC.

In 1852, the Julian calendar was modified by Pope Gregory XIII into the Gregorian calendar, which is the calendar we use today.



This material is licensed under the GNU Free Documentation License. It uses some information from the Wikipedia articles "Roman Calendar" and "Julian Calendar". The list of authors can be found here and here.