Asking about the date on which something happens using "effective"

How is the word "effective" or "effect" used to indicate from which date a new rule / change will be applied? I am not sure which of the following is correct:

These changes will take effect from March 1, 2012.
These changes will take effect on March 1, 2012.
These changes will be effective on March 1, 2012.
These changes will be effective from March 1, 2012.
These changes will be effective March 1, 2012.

Update: I just came across a new phrase:

March 1, 2012 is when the new changes will come into effect.

Hmm, I'd say #2 - #5 are all good and valid, while #1 is rarely used. If you say "take effect from" people would normally expect you to say "through" and give an end date. But for reasons that I don't think have anything to do with grammar, just convention, "be effective from" without an end date is common.

"... be effective on ..." is ambiguous. It could mean only that one day, or it could mean from that day until the indefinite future. People would probably guess from the context. Like if you said, "The new safety regulations will be effective on March 1", people would assume you meant from that day forward. But if you said, "The sale price will be effective on March 1", they'd probably think you meant just for that one day. "... be effective from ..." always means to the indefinite future.

Others have said that "be effective" can also mean "adequate to the purpose". True, but that would be an unlikely meaning when given with a date. If you said, "The new safety regulations will be effective", that would mean that they will, in fact, improve safety. But "The new safety regulations will be effection on March 1" means that's the day they start. I suppose you could imagine a casee where it's truly ambiguous. Like if someone is trying to say that the new safety regulations will be impractical when we install the new machine we're getting on April 1, I suppose he could say, "The new safety regulations will be effection in March", meaning they will be useful in March but will cease to be useful in April. But you could say that sort of thing about all sorts of words and phrases: they could have different meanings in different contexts. Lots of jokes are based on such potential confusion. As well as lots of unnecessary arguments, I suppose.

All are correct, but take effect is preferred to be effective. Take effect on seems most common:

"Changes will take effect on" also has more Google results than the other phrasings.