Safari doesn't sort array of objects like others browsers

var myArray = [{date:"2013.03.01"},{date:"2013.03.08"},{date:"2013.03.19"}];

I tried:

function(a,b){
  return b.date > a.date;
}

and

function(a,b){
  return b.date - a.date;
}

The console.log in Chrome and Firefox give me the desired output:

"2013.03.19", "2013.03.08", "2013.03.01"

but Safari give the original sorting:

"2013.03.01", "2013.03.08", "2013.03.19"

Why?