On 2011-6-29 the Google search page has the text "Your name is Galloping Gertie. How many furlongs long are you?" A portion of it is linked to "agoogleaday.com".
http://www.agoogleaday.com/
http://www.agoogleaday.com/#date=2011-06-29

And on the agoogleaday site is a popup explaining what "Deja Google" is.

I can't understand what they're getting at. If "Deja Google" is like the wayback machine, that would be great! If that was the case, Google could just say so.

Roger

There's a "What's that?" link at the top of the agoogleaday site that says:

<< You are searching Deja Google – A wormhole inspired time machine that enables you to solve today's puzzle spoiler free by searching the Internet as it existed before A Google a Day launched. >>

Also, on Google's official blog post about this it says:

<< To prevent spoilers from appearing as you search the web, look for the answers on agoogleaday.com instead of regular google.com—we’ve made a special version of Google that excludes real-time updates and other things that are likely to include spoilers as people post the answers to the puzzle online. >>

http://googleblog.blogspot.com/2011/04/trivia-game-where-using-google-is.html

Thank you mbegin. I saw the popup already, but it doesn't shed much light. And it somewhat contradicts the clearer explanation on the official blog post.

Is the index backdated, or does it just exclude real-time updates? Who knows? Who really cares?