I have a model with a convert function that takes a long and returns a date object

Code:
Ext.regModel('Data', {
    fields: ['id',
             'account',
             'amount',
             'category',
             {
               name: 'date',
               type: 'date',
               convert: function(v){ return new Date(v)}
             },
             'description']
});
When I try and use it in a template date is still returning the original long 1283403600000

Code:
    tpl: '<tpl for="."><div class="dataList">'+
                '<div class="amount">'+
                '{amount}</div>'+
                '{date}<br/>'+
                '{description}'+
            '</div>'+
         '</tpl>'
Some sample JSON

Code:
[{
     id: 2315,
     account: 3,
     amount: -15.88,
     category: "MISC",
     date: 1283403600000,
     description: "A"
},
{
     id: 2316,
     account: 3,
     amount: -38.42,
     category: "MISC",
     date: 1283403600000,
     description: "B"
},
{
     id: 2317,
     account: 3,
     amount: -23.72,
     category: "MISC",
     date: 1283490000000,
     description: "C"
}]
Any ideas what I'm doing wrong?