Yesterday was Veteran's Day, Veterans Day and Veterans' Day -- which means it was a very confusing day for people who take seriously the placement of their apostrophes.

The multi-volume U.S. Code, the book of federal laws, states without qualification that the holiday observed each Nov. 11 and known for years as Armistice Day is called Veterans Day, without punctuation. However, the index to the Code refers to it as Veterans' Day.

But, since it honors all veterans of all wars, the one thing the day is not is the singular Veteran's Day.

That would be news to advertisers in this and other newspapers. In yesterday's Washington Post, at least 13 advertisers in the "A" section alone, including such big firms as Raleighs and Levitz furniture, invited customers to a "Veteran's Day" sale. Hecht's was the larger of two that called it "Veterans' Day." Woodward & Lothrop and J.C. Penney were among eight that omitted apostrophes. Ads in the Baltimore Sun and New York Times also exhibited similar confusion.

Scotte Mann, the Post's advertising manager, said the ads -- some of them produced by the newspaper's own art department and some by the advertisers themselves -- were not screened for correct punctuation. "We will take steps to prevent it from happening again," she said.