sheet_to_calendar.gs

function scheduleShifts() {
  
  var spreadsheet = SpreadsheetApp.getActiveSheet();
  var calendarId = spreadsheet.getRange("A2").getValue();
  var eventCal = CalendarApp.getCalendarById(calendarId);
  
  var signups = spreadsheet.getRange("A5:D12").getValues();
  
  
  for ( x=0; x < signups.length; x++) {
    var shift = signups[x];
    var startTime = new Date(shift[0]);
    var endTime = new Date(shift[1]);
    var title = shift[2];
    var options = {
      description: shift[3]
    };
    console.info(shift);
    eventCal.createEvent(title, startTime, endTime, options);
  }
  
}


function onOpen() {
  var ui = SpreadsheetApp.getUi();
  ui.createMenu('Sync to Calendar')
      .addItem('Schedule shifts', 'scheduleShifts')
      .addToUi();

}