recordingsByDate.js

function recordingsByDate(recording_list) {

    // collapse data into a dictionary of Array's
    var dict = {},
        date = null;

    $(recording_list).each(function(i, val){
            date = this.YOUR_DATE_NORMALIZATION_FUNCTION(); // returns something like 'May 1, 2002'

            if(!dict[date]){
                dict[date] = [];
            }
            dict[date].push(this);
        });

    return dict;
}