I have searched high and low for this, and no doubt it is easy, but I would like to only show child pages if they are less than 7 days old. I have created a date field for the child page, etc., but how do I do maths on the date field easily, e.g.,
<% if $Date > ($Date.Now - 7 days) %> ... <% end_if %>
(I know I won't be able to do this in the template but it is easier to show the logic here than attempting to show the idea in PHP—at least for me it is)

function appropriatelyAged(){
	$this->Children()->filterByCallback(function($child){
		return date_create($child->date)->diff(date_create())->days < 7;
	});
}

Thanks