The set of Roman numerals used for writing calendar dates
- 1 = I (one); 5 = V (five); 10 = X (ten); 50 = L (fifty);
- 100 = C (one hundred); 500 = D (five hundred); 1,000 = M (one thousand);
- (*) 5,000 = (V) (five thousand); (*) 10,000 = (X) (ten thousand) - for future dates writing;
Note 1: (*) Number was also written with a bar above or between two vertical bars. We prefer writing of bigger numerals between brackets since on one hand it is more accessible to computer users and on the other it avoids the confusion between a vertical bar | and the Roman numeral I.
Note 2: (*) Romans did not use right from the beginning numbers larger than 3,999, so they were having no representation for numbers like 5,000, 10,000, 50,000, 100,000, 500,000, 1,000,000. These were later added and for them various different notations were used, not necessarily the ones above. Thus, initially, the maximum number that could be written with Roman numerals was: MMMCMXCIX = 3,999.