In Ext.data.writer.Writer method writeDate should be modified.


Not it is


Code:
    writeDate: function(field, date) {
        var dateFormat = field.dateFormat || 'timestamp';
        switch (dateFormat) {
            case 'timestamp':
                return date.getTime()/1000;
            case 'time':
                return date.getTime();
            default:
                return Ext.Date.format(date, dateFormat);
        }
    },
Should be:


Code:
    writeDate: function(field, date) {
        var dateFormat = field.getDateFormat() || 'timestamp';
        switch (dateFormat) {
            case 'timestamp':
                return date.getTime()/1000;
            case 'time':
                return date.getTime();
            default:
                return Ext.Date.format(date, dateFormat);
        }
    },
Problem is that field.dateFormat always returns "undefined";