Anybody knows what it depends on?

First is if they even offer it, many don't. Another is if they do offer it, do they have space at all? Another is dependent on your interview itself. For instance mine was a week early before my 3 year marriage PR. So I couldn't be sworn in officially for one more week so even if they did offer it, I wouldn't be able to. Also your interview might still need review so you would have to wait for others to look over your details even though you passed the initial interview etc...

I see. As far as time, I could of been USC almost 2 years ago, but they have delayed my I-751 for over 5 years...I just wondering how many and what circumstances took they oath right after the test.

Hi Warlord, does this mean you file N-400 way before the 3 year mark since the day you (or your spouse) became PR. They even processed it and interviewed you before that date too. That must be wonderful! (I've been taking the instruction in N-400 too literally and thought I could not start filing until the 3 year mark.)

Do you know if this is commonly accepted? ...Thanks

Sorry for the above hurried post. I've found helpful answers from here http://www.visajourney.com/forums/index.php?showtopic=84180
though I haven't located where in the M-475 file or on USCIS website they mention the the 90 days mark.

Was hasty again. Found it now, on bottom of page 22 in M-475, and again on page 34, and page 52.

And thanks, warlord, for the warning of filing right on the 90 day mark.

It's usually safe to wait a few days after the 90 day point begins. Some people have filed on exactly the 90 day mark and have had it retured to them which delayed them by several weeks. I waited a week or so and then filed...

I'm just curious about this because I saw you post it before and I've been meaning to ask and then forget every time...
How can they enforce something like this and get away with it when it is clearly stated by them on their guidelines that one can file 90 days prior the 3rd/5th anniversary of your PRS? I don't doubt it happened at all, (so please don't get me wrong I am not questioning your info about this )considering who we are dealing with, but I would guess any lawyer/congressman could have that easily reverted if they returned your application...it doesn't state anywhere that it has to be after or not on the 90th day, does it?
Just thinking that's all...