You must use mktime() function. It gives the amount of seconds between Jan. 1 1970 (timestamp). Then calculate 60 dates in seconds.
e.g.:
$now=mktime();
$past=(60 days in seconds);
$before60days=$now-$past;
Now use getdate() to convert timestamp to real date:
$60_days_ago=getdate($before60days);
This giving an array (check PHP functions):
$year=$60_days_ago[year];
$month=$60_days_ago[mon];
$day=$60_days_ago[mday];
$60days=$60_days_ago[year]."/".$60_days_ago[mon]."/".$60_days_ago[mday];
(must be like your date record)
Now in sql select query make a where clause to ask records greater than $60days.