code: function toDateTimeOptions(options, required, defaults) {
    if (IS_UNDEFINED(options)) {
      options = {};
    } else {
      options = TO_OBJECT(options);
    }
  
    var needsDefault = true;
    if ((required === 'date' || required === 'any') &&
        (!IS_UNDEFINED(options.weekday) || !IS_UNDEFINED(options.year) ||
         !IS_UNDEFINED(options.month) || !IS_UNDEFINED(options.day))) {
      needsDefault = false;
    }
  
    if ((required === 'time' || required === 'any') &&
        (!IS_UNDEFINED(options.hour) || !IS_UNDEFINED(options.minute) ||
         !IS_UNDEFINED(options.second))) {
      needsDefault = false;
    }
  
    if (needsDefault && (defaults === 'date' || defaults === 'all')) {
      %object_define_property(options, 'year', {value: 'numeric',
                                                writable: true,
                                                enumerable: true,
                                                configurable: true});
      %object_define_property(options, 'month', {value: 'numeric',
                                                 writable: true,
                                                 enumerable: true,
                                                 configurable: true});
      %object_define_property(options, 'day', {value: 'numeric',
                                               writable: true,
                                               enumerable: true,
                                               configurable: true});
    }
  
    if (needsDefault && (defaults === 'time' || defaults === 'all')) {
      %object_define_property(options, 'hour', {value: 'numeric',
                                                writable: true,
                                                enumerable: true,
                                                configurable: true});
      %object_define_property(options, 'minute', {value: 'numeric',
                                                  writable: true,
                                                  enumerable: true,
                                                  configurable: true});
      %object_define_property(options, 'second', {value: 'numeric',
                                                  writable: true,
                                                  enumerable: true,
                                                  configurable: true});
    }
  
    return options;
  }
docs: Returns options with at least default values in it.