I need to Display same date every month

Kindly Find this Screen shot
How to dsiplay the same date every month .
I used this code
function convertDays($days){
return $seconds = $days * 86400;
}

/**
* Convert a number of months into UNIX timestamp seconds
* @param int months : Number of months
* @return int seconds : Lenght of number of days in seconds
*/
function convertMonths($months){
return $seconds = $months * 2635200; // Seconds for 30.5 days
}

and I called timestamp() ;at the opening of every page
Kindly Help me with this issue.