How do you write the year 2013 correctly using Roman numerals?

Explanation

2013 (MMXIII) was just a regular Gregorian calendar year and started on an ordinary Tuesday. In the traditional Armenian calendar it was the year 1462. It was year 2557 of the Buddhist calendar. The Hebrew calendar is 6 minutes and 25 seconds longer than the solar year. Hence it was not until the 4th of September 2013 we entered year 5774 in the Hebrew calendar.