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.