I know it like I know the back of my... oh, wow.

Yahoo News (AP) | Library Clock Has 'IIII' Instead of 'IV'
GARDNER, Mass. - Library director Gail Landy learned that when it comes to Roman numerals on clocks, IIII equals IV.

Construction manager Tom Kondel, head of the Levi Heywood Memorial Library project, came to her recently and said, "Gail, we've got a problem with the clock," referring to the large clock installed over the west door of the new library building.

As Kondel said, the number four on the clock was IIII instead of the expected IV. Landy decided it wouldn't do to have what she called "an illiterate" clock.

"We called up the clock manufacturer and they said, `That's the way we do clocks,'" she told the Telegram & Gazette of Worcester in an interview published Friday.

When she looked at her watch, which had Roman numerals, she discovered that it too used IIII for the number four.

Actually, it may be of note that the AP reporter used Wikipedia as a source.