Some celebrate June 28th
Some do it on October 22nd
CAPS LOCK DAY is 20 years old.
by software developer Derek Arnold on Oct. 22, 2000, with this explanation, posted on a now-disabled webpage:
International Caps Lock Day is in fact a testament to the small mindedness of certain Western individuals: the majority of the world’s population writes in scripts which have no concept of letter casing. Therefore it is advised to laugh at anyone who invokes this day as an excuse to dismiss local typographical conventions: they are simply making an ass out of themselves.
It's also the special day on which we make that extra effort to annoy our Internet friends and co-workers and run afoul of case-sensitive passwords by abusing what, in some circles, is called the "Billy Mays" key — so named for the unmodulated pitchman Billy Mays, who passed away on June 28, 2009. It is in Mays' honor that Arnold added the second International Caps Lock Day to the calendar."
The second October date was added in memory of pitchman Billy Mays from Pennsylvania.