How do you say the number eight in Latin?

Annus MMDCCLXI AUC

The Roman numerals = 2761. AUC is abbreviation for Ab Urbe Condita - that's 'After the Founding of the City (Rome).

Romans reckoned dates from the date of the founding of Rome, which was 753 B.C. To convert to our calendar, add 753 to the year. 2008 + 753 = 2761.

If you mean "what are the ROMAN numerals for 2008?" the answer is MMVIII.