SELECT * FROM (`tabl1` as ap)
WHERE (ap.fromdate BETWEEN "2015-11-20 11:00:00" AND "2015-11-20 12:00:00")
AND (date('Y-m-d H:i:s',strtotime(ap.fromdate)+3600)
BETWEEN "2015-11-20 11:00:00" AND "2015-11-20 12:00:00")
use DATE_ADD
or INTERVAL
DATE_ADD(NOW(), INTERVAL 1 HOUR)
or
NOW() + INTERVAL 1 HOUR
if your date time coloumn name is ap.fromdate
use this :-
ap.fromdate + INTERVAL 1 HOUR