What do you notice about the three programs listed above? Hmmmm…?
If you said that two have apostrophes and one does not, you deserve a cookie.
But why was one neglected when the apostrophes were handed out?
I’m glad you asked. By a joint decision of a team of writers, proofers, and editors in 2002, it was agreed that Founders’ Day and Freshman Parents’ Weekend (which became First-Year Parents’ Weekend and is now Parents’ Weekend) would be plural possessive instead of just plural (i.e., Founders’ instead of Founders, and Parents’ instead of Parents).
Think of Founders’ Day as a day that “belongs” to the UW’s founders because we honor them (i.e., they “possess” the day), and there was more than one founder — thus, plural possessive instead of singular possessive. Likewise, think of Parents’ Weekend as a time that “belongs” to parents because we plan special programs for them (again, they “possess” it), and there is more than one parent who attends. If there isn’t, we’re in big trouble.
Grandparents University® followed the same thinking for a number of years (as Grandparents’ University), but when it was registered in 2007 — thereby earning its ® — somehow it came out the other side of the process without its plural possessive apostrophe. Now it’s just Grandparents University (plural, not plural possessive).