Fill the startDate, startTime, endDate, and endTime inputs at modify event view in Calendar app.

fill-data-time-input

[
  { selector: 'input[name="startDate"]', value: '2014-04-16' },
  { selector: 'input[name="startTime"]', value: '23:20' },
  { selector: 'input[name="endDate"]', value: '2014-04-17' },
  { selector: 'input[name="endTime"]', value: '01:20' }
].forEach(function(item) {
  var hackElement = document.querySelector(item.selector);
  hackElement.value = item.value;
  hackElement.dispatchEvent(new Event('input', {
    'view': window,
    'bubbles': true,
    'cancelable': true
  }));
});