function myFunction() {

/**
 *
 *   Test function for free times on a room.
 *
 */

function testGetRoomFreeTimes() {

  var roomId = "riotgames.com_53544c2d4e617574696c7573@resource.calendar.google.com";

  // Set the date to check for room free time slots
  var year = 2014;
  var month = 10; // October
  var day = 25;

  freeSlots = getFreeTime(roomId, year, month, day);
  Logger.log(freeSlots); // Returns [08:30-10:00, 11:00-14:00, 15:00-16:30]
  Logger.log('Number of free slots: ' + freeSlots.length); // Number of free slots: 3

  var totalSeconds = getTotalTimeRangeInSeconds(freeSlots);
  Logger.log('Number of free hours: ' + totalSeconds/3600); // Number of free hours: 6

};

/**
 * Returns Array of strings of Free time ranges for a given room on a given date.
 *@param{String} ex: roomId = "username@group.calendar.google.com".
 *@param{Nunber} Year of date to look up, ex. 2014.
 *@param{Nunber} Month of date to look up, ex. 10 for October.
 *@param{Nunber} Day of date to look up, ex. 12.
 *@return{Array} Array of free time strings. ex. ["08:30-10:00", "11:00-14:00", "15:00-16:30"].
 */

function getFreeTime(roomId, year, month, day) {

  var freeSlots = [];

  var calendar = CalendarApp.getCalendarById(roomId);

  // Set the standard start and end times for a room's day
  // example start 8:30, end 5:30.
  var roomStartHour = 8; // 24 hr time
  var roomStartMinute = 30; // 24 hr time
  var roomEndHour = 12+5; // 24 hr time
  var roomEndMinute = 30; // 24 hr time

  var theDate = new Date(year,month-1,day); // month is zero based

  var roomStartTime = new Date(year,month-1,day, roomStartHour, roomStartMinute, 0).getTime()/1000;
  var roomEndTime = new Date(year,month-1,day, roomEndHour, roomEndMinute, 0).getTime()/1000;;

  var lastTime = roomStartTime;

  var freeStr;

  var events = CalendarApp.getDefaultCalendar().getEventsForDay(theDate);
  Logger.log('Number of events: ' + events.length);

  for (var i = 0; i < events.length; i++) {

    var startTime = events[i].getStartTime().getTime()/1000
    //Logger.log(getFreeTimeStr(lastTime, startTime));

    freeStr = getFreeTimeStr(lastTime, startTime);
    if (freeStr) freeSlots.push(freeStr);


    lastTime = events[i].getEndTime().getTime()/1000
  }

  //Logger.log(getFreeTimeStr(lastTime, roomEndTime));
  freeStr = getFreeTimeStr(lastTime, roomEndTime);
  if (freeStr) freeSlots.push(freeStr);

  return freeSlots;
}

/**
 * Gets Free time string, or empty string.
 *@param{Nunber} Time elements to compare in unix time format.
 *@param{Nunber} Time elements to compare in unix time format.
 *@return{String} The free time string. ex. 08:00-13:00.
 */
function getFreeTimeStr(lastTime, thisTime) {
  var date, hours, minutes;
  var str = "";

  if (lastTime < thisTime) {
    date = new Date(lastTime*1000);
    hours = "0" + date.getHours();
    var minutes = "0" + date.getMinutes();
    str = hours.substr(hours.length-2)+":"+minutes.substr(minutes.length-2);
    str += "-";
    date = new Date(thisTime*1000);
    hours = "0" + date.getHours();
    var minutes = "0" + date.getMinutes();
    str += hours.substr(hours.length-2)+":"+minutes.substr(minutes.length-2);
  }

  return str;
};

/**
 * Goes through the array of time ranges and calculates total time in seconds.
 *@param{Array} Array of time ranges as strings. ex. ["08:30-10:00", "11:00-14:00", "15:00-16:30"]
 *@return{Number} Total seconds of all ranges.
 */
function getTotalTimeRangeInSeconds(freeSlotsArray) {

  var seconds = 0;

  for (var i=0; i < freeSlotsArray.length; i++) {
    seconds += getTimeRangeInSeconds(freeSlotsArray[i]);
  }

  return seconds;
};

/**
 * Calculates number of seconds in a time range string.
 *@param{String} Expects time range as string of given format. ex. "08:30-10:00".
 *@return{Number} Total seconds of this range.
 */
function getTimeRangeInSeconds(timeRangeStr) {
  var elems, subElems;
  var startTime, endTime;
  var hours, minutes;

  elems = timeRangeStr.split("-");
  subElems = elems[0].split(":");
  hours = subElems[0];
  minutes = subElems[1];

  startTime = ((hours * 60 * 60) + (minutes * 60));

  subElems = elems[1].split(":");
  hours = subElems[0];
  minutes = subElems[1];

  endTime = ((hours * 60 * 60) + (minutes * 60));

  return(endTime - startTime);

};}