IIII vs IV
Why modern canonical form prefers IV over IIII—and when clocks still use IIII.
What is wrong
I should use subtractive notation before V for 4 (IV).
Canonical form
IV is produced by this site’s conversion engine for 4.
Clock faces
Many clock dials use IIII for 4. That is a well-known dial convention and differs from the modern canonical teaching form IV. There is no single universally agreed historical reason that explains every dial; treat IIII-on-clocks as a convention, not as the converter standard. See Roman numerals on clocks.