How to Write Dates in Roman Numerals

A date is three numbers, and each one is converted on its own:

• the day, 1 to 31: I to XXXI;
• the month, 1 to 12: I to XII;
• the year, written in full: 1990 = MCMXC, 2026 = MMXXVI.

Leading zeros disappear because Roman numerals have no zero. 09 is IX, 05 is V. Don't try to write "0" in front.

Worked example, 25 December 2026: 25 = XXV, 12 = XII, 2026 = MMXXVI, so XXV.XII.MMXXVI in day-month-year order.

The order is the part people get wrong, because it changes from country to country. The Unicode CLDR, the shared database of locale conventions, keeps a date pattern for each locale, and its documentation shows the difference: English medium dates go month-day-year, German goes day-month-year and Japanese goes year-month-day (CLDR). Here is 11 November 2026 in the short format of each locale, as CLDR orders it:

If the date is for someone in another country, use their order, or the international standard. ISO 8601 writes dates "in a fixed order from the largest to the smallest unit", YYYY-MM-DD, precisely "to remove the confusion caused by the many different date and time formats used worldwide" (ISO). In Roman numerals that gives MMXXVI-XI-XI.

The parts need something between them, or XIXIMMXXVI becomes unreadable. Common choices are:

• dots: XI.XI.MMXXVI
• middle dots: XI·XI·MMXXVI
• hyphens: XI-XI-MMXXVI
• spaces or line breaks, for a tattoo or a ring with three lines

Any of them works as long as you use the same one throughout. The slash is the least clear, because it reads like a fraction.

"90" for 1990 becomes XC, which looks like a complete number, not a year. A reader can't tell XC from 90 AD, 1990 or 2090. Write the year in full.

Split the date at the separators, convert each part and only then decide which one is the day and which the month:

• XXV.XII.MMXXVI: XXV = 25, XII = 12, MMXXVI = 2026. The first part is above 12, so it can only be the day: 25 December 2026.
• VII.IV.MCMXC: VII = 7, IV = 4, MCMXC = 1990. Both 7 and 4 could be a month, so this is 7 April 1990 in day-month order and July 4, 1990 in US order. Without context, you can't tell.
• MMI-IX-XI: MMI = 2001 can only be a year, so this is year-month-day: 11 September 2001.

When a date could go either way, use the order of the country where it was written (see the table above), or ask the person who wrote it.

A date in Roman numerals is easy to get wrong in a way nobody notices until later. Before it goes on skin, metal or stone:

1. Confirm the order with the person it's for: 04.07 is April 7 in the US and 4 July in the UK.
2. Convert each part separately and check it with the validator. The classic errors are IIII for 4 and IL for 49.
3. Write the year in full, never "XC" for '90.
4. Choose one separator and use it everywhere.
5. Read it back from Roman to digits, out loud, before you approve the design.

• 1 January 2000: I.I.MM
• 29 February 2024 (a leap day): XXIX.II.MMXXIV
• 14 March 1879, US order: III.XIV.MDCCCLXXIX
• 31 December 1999, ISO order: MCMXCIX-XII-XXXI

For a single year, see the year converter or the list of years.