The starting point of limitation is the date of knowledge of the alleged fraud

1996(7) SCC 767

 (Noorul Hoda vs. Bibi Raifunnisa)

6. " ........................ The starting point of limitation is the date of knowledge of the alleged fraud. When the plaintiff seeks to establish his title to the property which cannot be established without avoiding the decree or an instrument that stands as an insurmountable obstacle in his way which otherwise binds him, though not a party, the plaintiff necessarily has to seek a declaration and have that decree, instrument or contract cancelled or set aside or rescinded