To write regular expression for dd/mm/yyyy format
[0-3][0-9][/](([0][0-9])|([1][0-2]))[/][0-9]{4}

The above regular expression(Ans:1) will fail as it allows 
day between 31 to 40 as well.

The following regular expression takes care of all cases 
and validate the format (dd/mm/yyyy)  

(0[1-9]|[12][0-9]|3[01])/(0[1-9]|1[012])/\d{4}

[0-9]+//[0-9]+//[0-9]+
use this buddy...