check if its one hour before time

[youngnoviceinneedofh]

So I am trying to check if the current time is one hour before a variable time:

$date_game=$dt->format('Y n j'.$pieces[2]);
echo $date_game;
echo date('Y n j H');

if (date('Y n j H') < $date_game)  {
echo "The time is before the stored time";
}

This displays
2012 1 21 17:30
2012 1 21 16
i.e $pieces[2] = 17:30. and $dt formatted Y n j = 2012 1 21.
The current Y n j H is 2012 1 21 16.
I want to know if it is more than one hour until the date/time stored in $date_game.

At the moment it just tells me that it is before that time.
Can I do something like

$data_game - 1->format('H');

or something?
Thanks guys