roman numerals on a clock face

[glenis]

why are they upside down when they get to 6 ? this dosn't happen on a clock face with arabic numbers

[Octavius]

For the appearance of symmetry. Similarly you'll see the 4 as IIII rather than IV.

[Quizmonster]

Clock-faces with Roman numerals usually represent 4 by IIII rather than IV. This is generally taken to be so that the four elements of the number better balances the four elements of VIII for 8 on the same level at the other side, as Octavius says.
However, the clock-faces on the �Big Ben' tower at the Palace of Westminster - probably the best-known such clock-face in the entire world - actually uses IV for 4! Click here for a close-up picture of it. It shows clearly - though almost upside-down - that the 4 is IV and not IIII.