I usually like to release press releases on Mondays or Tuesdays, however the second anniversary of one of my sites is coming up, and it happens to be on a Saturday. I'm thinking that I definitely need to release a press release on Friday, a day before the anniversary, or possibly even on Thursday. What do you guys do when news happens on the weekend? Would you wait till Monday or would you put it out on Thursday or Friday?
Release it early and use an embargo if you really want. So long as the journo has it in time to write the article... they can schedule it for publication a few days forward. If you are still unsure, ring the journo and outline the story and ask them when they want the release.
You can always release a press release 1 week to go before anniversary then release and then a press release on actual anniversary
Simply news of a website having an anniversary isn't a good enough news angle on its own. Are you doing something special to celebrate it? If so, make that more of an angle, and stretch the celebration (could be anything from a discount to a contest to giving something away for free; even just an ebook or something) over more than just Saturday. Then send the release out at least a few days beforehand.