Make it permanent and see how things pan out.

Killa, the server may be run out of Europe, but a large percentage of it's players are based in North America

Not my place to say it but to commemorate the day surely the suggested disability of talk (for a minute) and increased chance of freebies for a few hours. This would replace having to sell past items for lower prices, but a token item/hat would be great to mark the day.