I could be wrong, but I do know that the earliest festival of the year is the Laguna Beach Music Festival. I've never been, but heard it's a great deal of fun. The latest festival I've seen is in the month of October.
Before I had a child my wife and I always kept up with what was current. We would hit every music festival there was even if the music wasn't one we particularly vibed out to. We would discover new artist and styles of music whenever we could. Now there are so many. Even if we tried to keep up, we'd miss a few because they're everywhere all the time.
“I've never been, but heard it's a great deal of fun.”