We know Star Wars happened, "A long time ago, in a galaxy far, far away". Is there any information on exactly when that was, relative to our time?
No. I think Lucas wanted to remove all links to our world. Though I found a decent Star Wars timeline explaining when the various events happen in the Star Wars universe.
The issue is one that the Star Wars Galaxy must have 3rd generation (Population I) stars to exist, meaning it's at least many billion years post-Big-Bang.
Given the current estimates of 13.75 billion years of age, it's likely it's not more than 8 billion years ago (BYA), in order to allow for the relatively modern shape portrayed in the films. Moreover, the Milky Way has lots of Population II stars, but those can't give rise to life as we know it in their worlds, as the needed high-metal mixtures won't be present to coalesce into terrestrial worlds until the nova of Population II stars forms sufficient metals to generate the population I stars which gave birth to us all. Note that the oldest Population I stars have less than 2% of the metal content, and that we are, as a life form, carbon, calcium and iron with significant smaller amounts of other stuff, but the lower metalicity of the older stars implies a lack of iron.
So, we can rule out the oldest. Getting to the 5 BYA point, we start looking at stars that might have life as we know it. Not so much heavy metals, but still, enough to have stuff we would recognize.
So, I'd say the "Galaxy Far Far Away" had its "long time ago" no more than 5 BYA and probably no more than 1 BYA, because it looks like galaxies of that age.
There is absolutely no way to pin this down. As Roger Ebert pointed out, we're not even necessarily the frame of reference to which the "A long time ago..." refers to. That is to say, this is all a story being told to us from an unseen narrator, from whose point of view the events of the story happened "a long time ago, in a galaxy far, far away."
Because we don't know where (or when) the narrator exists, we can't know where or when the events occurred. It could well be right around the corner, just a couple of years from now (or ago).
Star Wars Tales Volume 5 was a comic that was written a few years ago. According to its Wikipedia article:
Han Solo and Chewbacca are aboard the Millennium Falcon when they are attacked by Imperials. They are forced to leap to hyperspace blind and end up in our solar system, where they crash on Earth's Pacific Northwest. Believing they are on Endor due to the large trees, they venture out to investigate, when Han is killed by Native Americans. The mourning Chewbacca leaves the Falcon to live in the trees, where the natives believe him to be Sasquatch. 126 years later, the wreckage of the Falcon and Han’s remains are found by the intrepid American archaeologist Indiana Jones and his sidekick, Short Round. Indy, spooked by how 'eerily familiar' the remains are, decide to leave them in peace.
That would put it somewhere near 1800 because the adventures of Indiana Jones takes place in the '20s and '30s. I heard an unrelated story about it taking place 5,000 years ago, as well.
Unfortunately I can't remember where I read this and can't provide a reference. But I did read that Lucas originally planned for Star Wars to take place in our future, in the year 3000 or thereabouts. But then the idea struck to set it "A long time ago in a galaxy far, far away..." and Lucas realized it freed him from having to tie the history of Star Wars to our real history, he could simply make everything up from scratch. He didn't even really have to worry about being entirely faithful to the laws of physics (sound in space, gravity and breathing on an asteroid, etc.).
So no, Star Wars doesn't take place in "our" time at all, and that was a conscious choice. (Didn't stop me, as a kid, from thinking ROTJ would end with someone discovering Earth.)