Flexibility, how long!!!
It depends on your age and how much you kept up with your flexibility when you were younger. If you were able to do the splits after the age of 7 then you will be able to regain that flexibility much quicker than if you just started. For me, I was able to do the splits roughly 5 years ago and it took me about 2 months of stretching everyday to do it again (Im 21 btw). When I first started to do the splits it took about a year and a half. The older you get, the longer it takes-- for most people anyway.