We've all heard the saying "Beware the Ides of March" right? The saying, from Shakespeare's play Julius Caesar, was said by a soothsayer warning the Emperor of the coming assassination. While we have no evidence that Caesar was actually warned ahead of time, the Ides of March has most famously become associated with that fateful day.  While many people know that the Ides of March is the 15th of March, many don't know what it actually meant and what its role in the Roman calendar was.  Would it surprise you to know that the Ides of March was a sacred day long before Julius Caesar was assassinated. Each month on the Ides, the Romans sacrificed a sheep to the god Jupiter. There were also festivals dedicated to springtime and the new year that took place on this day.

The Roman calendar was a lunar based calendar, with several fixed dates during each lunar cycle. Special days were determined during the month that were considered lucky or unlucky, and auspicious days for festivals and rituals. The Romans didn't name their days in numerical order, but rather had a somewhat complicated system of counting forward to certain points during the month, and referring to the other days by the number of days until the fixed point.

The first day of every lunar cycle was called the calends (or Kalends), determined when the moon was a thin crescent. Yep, thats the root of the word calendar!  On that day, the pontifex minor would announce the number of days to the next new moon. From there, the Nones (generally corresponding to when the moon was a quarter full) would be calculated as the 7th day of full months (a 30 day lunar cycle) or 5th day of a hollow month (a 29 day lunar cycle). From there the Ides would be calculated 8 days after the Nones as the 15th day of full months and the 13th day of a hollow month, generally corresponding to the full moon in the middle of the month.

For example, the 10th day of March would be “5 days until the Ides of March.” The Romans were inclusive counters, meaning that they included the starting day and the final day in their calculations.

Roman numerals are a system of using letters from the Latin alphabet that each represent a fixed number and are combined in various combinations to create values. The letters are combined to indicate a larger number, for example, the number 3 is written III and and 300 CCC. Roman numerals are written like Arabic numbers with places, like thousands/hundreds/tens/one

Certain numbers are written using “subtractive notation” meaning that the number to the left is subtracted from the number to the right. For example, 4 is written IV not, IIII and 9 is written IX. Other “subtractive notations” are:

  • XL – 40
  • XC- 90
  • CD-400
  • CM-900

Other examples:

19 is written XIX (10, 9)

1900 is written MCM (1000, 900)

424 is written CDXXIV (400, 20, 4)


Grab a calendar and pick out some dates that are important to you – birthdays, holidays, anniversaries, and convert them into Roman dates using Roman numerals (remember to account for full months and hollow months!)

For example February 6, 2023: VIII days before the Ides of February MMXXIII

Play a short matching game with Arabic and Roman numerals. Print out the cards here.

Expand your knowledge of calendars using our Calendars Unboxed downloadable lesson! In this lesson you’ll…

  • Learn about why our weeks have 7 days
  • Make a mobile featuring the Roman and Norse history of weekday and month names
  • Play a card game and learn the Tsalagi (Cherokee) names of the month
  • Explore the included calendars and compare different cultures!
  • Dive deep with recommended reading about timekeeping traditions around the world

Want to learn more about Julius Caesar? Check out our Julius Caesar hands-on box where you’ll…

  • Weave your own laurel wreath
  • Listen to an audio version of Shakespeare’s play
  • Play a Latin card game
  • Color a picture of Julius Caesar

Check Out These Books to Learn More & Practice Converting to Roman Numerals!

  • Fun with Roman Numerals by David Adler
  • How Did Romans Count to 100? An Introduction to Roman Numerals: An Audiobook About the Math of the Gladiators by Lucy D. Hayes
  • Roman Numerals I to MM: Liber De Difficillimo Computando Numerum by Arthur Geisert


Leave a Reply