hsp.js

var EVENT_NAME = prompt("Kursname eingeben");

var scrpt = document.createElement('script');
scrpt.src='https://rawgit.com/connorbode/ics.js/master/ics.deps.min.js';
scrpt.type = 'text/javascript';
document.head.appendChild(scrpt);

var scrpt = document.createElement('script');
scrpt.src='https://cdnjs.cloudflare.com/ajax/libs/FileSaver.js/1.3.3/FileSaver.min.js';
scrpt.type = 'text/javascript';
document.head.appendChild(scrpt);

setTimeout(createIcs, 1000);

Date.prototype.stdTimezoneOffset = function () {
  var jan = new Date(this.getFullYear(), 0, 1);
  var jul = new Date(this.getFullYear(), 6, 1);
  return Math.max(jan.getTimezoneOffset(), jul.getTimezoneOffset());
}

Date.prototype.dst = function () {
  return this.getTimezoneOffset() < this.stdTimezoneOffset();
}

function createIcs() {
  var table = document.getElementsByTagName('tbody') [0];
  var cal = ics();
  for (var i = 0; i < table.childElementCount; i++) {
    var row = table.childNodes[i];
    var date = row.childNodes[1].textContent.split('.');
    var isoDate = date[2] + '-' + date[1] + '-' + date[0];
    var diff = ((new Date(isoDate)).dst()) ? -2 : -1;
    var time = row.childNodes[2].textContent.split('-');
    var from = time[0];
    var to = time[1];
    var fromSplit = from.split(':');
    var toSplit = to.split(':');
    var isoFrom = isoDate + 'T' + (parseInt(fromSplit[0])+diff) + ':' + fromSplit[1];
    var isoTo = isoDate + 'T' + (parseInt(toSplit[0])+diff) + ':' + toSplit[1];
    var loc = row.childNodes[3].childNodes[0].textContent;
    cal.addEvent(EVENT_NAME, '', loc, isoFrom, isoTo);
    console.log('Am ' + date + ' von ' + isoFrom + ' bis ' + isoTo + ' in ' + loc);
  }
  cal.download(EVENT_NAME);
}