Encoding datetime for JSON consumers like YUI

Passing datetimes from Python to a YUI DataTable via JSON served by django-piston turned out to be surprisingly rocky. This code actually works with YAHOO.lang.JSON.stringToDate (not YAHOO.util.DataSource.parseDate) which cannot handle time zone specifiers other than "Z" or dates without timezones.

The YUI DataSource which uses this looks something like this - note that simply setting format:"date" does not work as that uses YAHOO.util.DataSource.parseDate, which usesDate.parse to do the actual conversion, which will involve browser-specific formats and as of this writing only Chrome's native Date can reliably parse ISO 8601 dates.

myDataSource.responseSchema = {
    resultsList: '…',
    fields: [
        …
        {
            key: 'my_date_field', 
            parser: YAHOO.lang.JSON.stringToDate
        },
    ],
    …
};