var diff =
new Date( '01/01/2009 ' + $('#fTime').val()) -
new Date( '01/01/2009 ' + "03:00 PM" );
var hours=(diff / 1000)+"";//just to make it a string
var mins=(diff / 1000 / 60 )+"";
var diff_time=hours+":"+mins;
use diff_timehours+":00"
for outputs like "22:00" hrs
Also, find the time format should have a AM/PM