Question: how old are the mlp?
Answer: Applejack: 23-24; Rarity: 22-23; Fluttershy and Rainbow Dash: 21-22; Pinkie Pie: 20-21 (a year younger than Fluttershy); Twilight: 18-19; The entire series so far seems to have taken a little over a year, and RD had a birthday in Pinkie Pride, so they've probably all aged a year since season 1.