...to me. Yesterday, October 3, marked the Xth anniversary of my retirement from the defense think-tank where I had worked for 30 years. I won't dwell on the reasons for my joy at retiring -- but it was a joyous event. So, happy belated anniversary to me.
P.S. You will note that I wrote "Xth anniversary," not "X-year anniversary" in the contemporary way. "Anniversary," according to The Living Webster Encyclopedic Dictionary of the English Language (1975 edition), means a "stated day on which some event is annually celebrated." The Latin roots of the word are annus, a year, and verto, versum, to turn. Thus, the literal meaning of "anniversary" is "returning with the year at a stated time."
The construction "X-year anniversary" has arisen because it has become common to denote the passage of less than a year since an event as an "X-month anniversary." Only a person who is completely ignorant of the meaning of "anniversary" -- or a person who is unwilling to stand up to the forces of lexical barbarity -- could say "X-month anniversary." As for "X-year" anniversary, it's wrong because it's redundant; "anniversary" itself denotes the passage of years.
There's only one way to say it correctly, and that's my way: "Xth anniversary."