I'm a tad confused...

So I recently re-watched "Apple Family Reunion" and I noticed something that's gotten me a bit confused.

So according to Granny Smith the family reunion takes place once every one-hundred moons.

To my knowledge one moon is the equivalent of one month.

We also saw that when Twilight first came to Ponyville, she visited AppleJack during an Apple family reunion.

So if the reunion is every one hundred months which is equal to eight years and four months....does that mean that it's been eight years since the season 1 opener?

If anyone can shed more light on this thing please do, because if that's the case, I'm pretty sure that the mane 6 and Spike would look a good bit older.