While I agree, and even had that thought myself; this is further into that paragraph.
It goes on to reference them spending time with him, and then later sneaking out of the Shrieking Shack.
Originally Posted by POA, US paperback p 354
"Peter needed all the help he could get from James and Sirius. Finally in our fifth year, they managed it."
That means it was close to the beginning portion of the year, IMO.
Perhaps James and Sirius became animagi at the end of their fourth year and finally Peter got it during 5th year? When you look at the quote Red Haired Mom posted it makes it seem as though only Peter managed it during 5th year. Except that 'they'. or I don't know when Sirius left home and stayed with James but if it was at a young age then maybe James and Sirius could have worked on becoming animagi over the summer at the Potter's. They wouldn't have to worry about a trace because James's parents were wizards. In one of the books it says that the trace is not on children in wizarding households because their parents are expected to control them. So, If James and Sirius had become animagi over the summer then that could still be considered 5th year.
I was always under the impression that WW happened after SWM. During SWM it doesn't seem like there is any more tension between MWPP and Snape other than their usual hatred of each other. If it was after WW I think that it would be a lot more intense. Also, I doubt that Sirius would say "I'm bored, I wish it were full moon" after WW. If it had happened any where during 5th year I think that there would still be issues with Sirius' decision to tell Snape and their referencing the full moon. Remus and James might be angry at him for that and overall I think this comment would have recieved a different reaction. Another thing, James would have had to have matured a little to want to help Snape, and he was still quite immature in 5th year. And finally, In DH we see Snape talking with Lily after SWM, I think he would have said something about that incident regardless of how embarrassing it was for him. He was desperate to keep Lily and I could see him using something like WW to prove that the Marauders aren't that great of people.
It just seems like WW had a very large impact on the relationship between MWPP and Snape. Like they would be more distant and MWPP would be less cruel to him. And being less cruel to him does not include suspending Snape in the air.
We actually had an extended debate about this in the MWPP summer term class. The facts that we have are that WW happened before SWM, but they were both in fifth year. And it is canon that the Marauders became Animagi in fifth year. We just are not told when. The confusion is not whether WW happened before SWM or how it affected their relationships, it's only whether or not James, Sirius, and Peter were Animagi when WW happened.
Unfortunately, the closest thing to canon evidence we have is Snape's memories in DH, and he obviously was not privy to the secrets of the Marauders, so his evidence tells us nothing about whether or not the Marauders were Animagi at the time he was tricked into following Remus into the Shrieking Shack.
Fawkes_the_Phoenix, we actually had ample reason to suspect that WW only made SWM worse, but it was a very long discussion. If you're interested, please check out the first week's discussion on James Potter in "MWPP: A History" in the classes forums. ^_^ Too many people made too many good points for me to attempt to set them down here, especially when it's not really relevant to the question posed.