How to Convert Roman Numerals to Dates

Roman numerals, as seen on this clock face, use letters to represent numbers.

Roman numerals were developed centuries ago to indicate quantities in trade. In this system, letters are used to represent a different number in factors of tens and fives: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000. There are no zeros in Roman numerals. Additionally, the last number before the next step up in letter symbols is indicated with a smaller number symbol in front of the larger one. For example, four is represented as IV, not IIII; similarly, 1900 is represented as MCM, not MDCCCC.



Roman numerals, while attractive, are impractical for large calculations. Today they are commonly used decoratively on clocks, in pages of book introductions, in outlines, to indicate people or ships that share a name and as dates on tombstones and copyrights.

Things You'll Need

• Calculator

Instructions

Year

1. Write the Roman numeral grouped with a space between the different letters. Group any numerals smaller than the following numeral together. For example, MDCCLXIV would be M D CC L X IV.

2. Count the number of each letter and multiply by its value. For example, MDCCLXIV would be M = 1 x 1,000, D = 1 x 500, CC = 2 x 100 = 200, L = 1 x 50, X = 1 x 10, IV = 5 - 1 = 4.

3. Add the numbers together. This results in the date. For example, MDCCLXIV would be 1,000 + 500 + 200 + 50 + 10 + 4 = 1764.

Month

1. Write the Roman numeral grouped with a space between the different letters. Group any numerals smaller than the following numeral together. Because there are only 12 months, the only numerals used will be X, V and I. For example, XII would be X II.

2. Count the number of each letter and multiply by its value. For example, XII would be X = 1 x 10, I = 1 x 2 = 2.

3. Add the numbers together. This results in the number of the month. For example, XII would be 10 + 2 = 12.

4. Assign the number of the calendar month to the number. For example, 12 would be the 12th month, which is December.

Day

1. Write the Roman numeral grouped with a space between the different letters. Group any numerals smaller than the following numeral together. Because no month has more than 31 days, the only numerals used will be X, V and I. For example, XXIX would be XX IX.

2. Count the number of each letter and multiply by its value. For example, XXIX would be X = 2 x 10 = 20; IX = 10 - 1 = 9.

3. Add the numbers together. This results in the number of the month. For example, XXIX would be 20 + 9 = 29. This is the number of the day. In the final example, the date is Dec. 29, 1764.

Tips & Warnings

• Most of the time, Roman numerals are used only for the year. In rare situations, however (like on the Statue of Liberty's tablet, which reads "July IV, MDCCLXXVI"), the day of the month is in Roman numerals.

• In some countries, the number of the month is given as a Roman numeral to avoid confusion between that and the day of the month.

References

• Nova Roma: On Roman Numerals
• Kent State University: Roman Numerals Chart
• RomanNumerals.co.uk: Roman Numerals List Chart
• National Parks Service: Statue of Liberty Frequently Asked Questions

Resources

• OnlineConversion.com: Advanced Roman Numeral Converter
• Stephanus Gibbs: Roman Numeral and Date Conversion with Roman Calculator & Roman Numerals Test