docs: function getDateGroup (date) {
    var d = new Date(date);
    var year = d.getFullYear();
    var month = d.getMonth() + 1;
    var day = d.getDate();
    var groups = [];
    groups.push('' + year);
    groups.push('' + year + '-' + (month < 10 ? '0' : '') + month);
    groups.push('' + year + '-' + (month < 10 ? '0' : '') + month + '-' + (day < 10 ? '0' : '') + day);
    return groups;
  }