The Chicago Manual of Style lists the following holidays as singular possessives: Mother’s Day, Father’s Day, New Year’s Eve, New Year’s Day. Plural possessive is used for Presidents’ Day.
Your guess is as good as anyone’s about Secretary’s vs. Secretaries’ vs. Secretaries Day and Boss’s vs. Bosses’ vs. Bosses Day.
What would you do if we had a Children’s Day holiday? Because Children is an irregular plural (not formed by adding an s or es), you would have to use the apostrophe in the title because there is no such word as Childrens.
Example: Children’s Hospital
Posted on Thursday, December 11, 2008, at 7:00 pm