When DD was at the Y, we went to some Y meets and some USAG meets. The season was pretty similar, with meets from late fall to early spring. I know USAG schedules are different from state to state... I don't know if The YMCA meet season is the same nation-wide or if each state sets their own schedule. Her team never did Nationals, but yes, they're in the summer.
YMCA meets run the same season generally as USAG. I think every state would have to be similar because Y nationals are the end of June. Generally Y states are around the same time as USAG states, not the same weekends obviously, because then you couldn't do both, if your team does both.
It depends on the Y. Some Y's are more competitive than others. Our Y is among the more competitive ones and we compete USAG only. We also go to states, regionals and nationals.
The YMCA Gymnastics Nationals is a summer meet that tends to be a very fun meet that has no bearing on USAG qualifiers. We did not compete the compulsories this year because of the change in routines and did not want to hang onto the old routines until the end of June. The Optionals did go and did quite well.
there are some Y's that only do AAU, and attend very local meets i order to give their participants a better experience that is less competitive, BUT it depends.
We begin the season September, stats are in November/December.