Learn the values for the Roman numerals and how they work first. "M" equals 1,000, "D" equals 500, "C" equals 100, "L" equals 50, "X" equals 10, "V" equals five, and "I" equals one. The letters in a Roman numeral add together to make the number. Some letter combinations subtract values to create an individual number before adding the number to the total.
Use capital Ms to stand for each thousand in a date. For dates in the 2000s, write two Ms to begin the year--"MM" stands for 2,000. For dates in the 1000s, write one M to stand for 1,000.
Use X, C, and D to represent the hundreds in a year. For dates in the 20th century (1900s), write "MCM." For dates in the 1800s, write "MDCCC." Dates in the 1700s have "MDCC," the 1600s have "MDC," the 1500s have "MD," and the 1400s have "MCD."
Represent the tens in a year with X, L, and C. For example, the year 1941 uses an "XL" to represent the "40" (50 - 10 = 40). The year 1872 uses "LXX" to represent the "70" (50 + 10 + 10 = 70).
Represent the ones in a year with I, V, and X. For example, the year 2010 would simply be "MMX" because there are no zeros in Roman numerals. The year 2011 would be "MMXI," with the "XI" making 11 (10 + 1 = 11). The year 1978 uses "VIII" to make up the final eight (5 + 1 + 1 + 1 = 8).
Place all the letters together to make the year. For example, in Roman numerals, the year 1997 is "MCMXCVII." "M" represents the one (the thousand). "CM" represents the first nine (900) because "C" represents 100 (subtracting 100 from 1,000: CM equals 1,000 - 100, or 900). "XC" represents the second nine (90) because "X" represents 10 (subtracting 10 from 100: XC equals 100 - 10, or 90). "VII" represents seven because "V" makes five and each "I" makes one (5 + 1 + 1 = 7). M + CM + XC + VII = 1997. Make the year 1492 with "MCDXCII." "MCD" represents 1400, "XC" represents 90, and "II" represents two--MCD + XC + II.