Long term captial gain reinvestment

I booked a apt in 2013 and got it registered in 2018 (Prop A). I sold another property in 2018 (Prop B). Can I claim long term capital gain on sold property (Prop B) as I got my apt (Prop A) registered in same year since it is less than 1yr of selling (Prop B). What is the ownership defined? Did I become the owner of (Prop A) in 2013 or after registtation?