lib/Ext/field/DatePicker.js
function(newDateFormat, oldDateFormat) {
        var value = this.getValue();
        if (newDateFormat != oldDateFormat && Ext.isDate(value)) {
            this.getComponent().setValue(Ext.Date.format(value, newDateFormat || Ext.util.Format.defaultDateFormat));
        }
    }
function(newDateFormat, oldDateFormat) {
        var value = this.getValue();
        if (newDateFormat != oldDateFormat && Ext.isDate(value)) {
            this.getComponent().setValue(Ext.Date.format(value, newDateFormat || Ext.util.Format.defaultDateFormat));
        }
    }
Updates the date format in the field.
@private