title: icalendar AssertionError: VTIMEZONEs sub-components' DTSTART must be of type datetime, not date
body: <p>When I run this code in Python 3.75, vscode:</p>
  <pre><code>from icalendar import Calendar 
  import requests
  SkeddaBridgeURL = 'https://bridgeartspace.skedda.com/ical?key=457bda7'
  f=requests.get(SkeddaBridgeURL)
  c = Calendar.from_ical(f.text)
  </code></pre>
  <p>I get this error:</p>
  <pre><code>VTIMEZONEs sub-components' DTSTART must be of type datetime, not date
    File &quot;/Users/jeff/Scrape/Code/skedda.py&quot;, line 6, in &lt;module&gt;
      c = Calendar.from_ical(f.text)
  </code></pre>
  <p>But when I run this URL through the ical validator at <a href="https://icalendar.org/validator.html" rel="nofollow noreferrer">https://icalendar.org/validator.html</a>, I get no errors.</p>
  <p>I don't feel qualified to call this a bug, but maybe it is!</p>
  <p>One way I have tried to deal with this is to suppress Assertion Errors by a startup flag as:
  <code>python 3 -Oc &quot;Assert False&quot;</code></p>
  <p>But I fail to see how to set this as a flag in VSCode, which I am also learning.</p>
  <p>Furthermore, running the debugger on this code, having installed <code>icalendar</code> via pip3, I cannot step into the code, or modify it.  Will I need to figure out how to download the entire module from github and go delete the assertion?</p>