static/ext/src/lang/Date.js
function(name) {
        // handle camel casing for English month names (since the keys for the Ext.Date.monthNumbers hash are case sensitive)
        return Ext.Date.monthNumbers[name.substring(0, 1).toUpperCase() + name.substring(1, 3).toLowerCase()];
    }
function(name) {
        // handle camel casing for English month names (since the keys for the Ext.Date.monthNumbers hash are case sensitive)
        return Ext.Date.monthNumbers[name.substring(0, 1).toUpperCase() + name.substring(1, 3).toLowerCase()];
    }
<locale type="function"> 
Get the zero-based JavaScript month number for the given short/full month name.
Override this function for international dates.
@param {String} name The short/full month name.
@return {Number} The zero-based JavaScript month number.