title: iCalendar daylight saving time
body: <p>I give my users a link they can use to put their appointments that are on my system in their calendar software like Outlook,... using an iCalendar URL.</p>
  
  <p>I generate the dates in the file using this code:</p>
  
  <pre><code>echo "DTSTART;TZID=" . date_default_timezone_get() . ":" . strftime('%Y%m%d', strtotime($app-&gt;app_start)) . 'T' . strftime('%H%M%S', strtotime($app-&gt;app_start)) . '' . $eol;
  echo "DTEND;TZID=" . date_default_timezone_get() . ":" . strftime('%Y%m%d', strtotime($app-&gt;app_end)) . 'T' . strftime('%H%M%S', strtotime($app-&gt;app_end)) . '' . $eol;
  </code></pre>
  
  <p>This always worked correctly. But now we're in daylight saving time and all the appointments that are in daylight saving time appear 1 hour too late in my Outlook. Appointments before DST are okay.</p>
  
  <p>So, for example in my ics:</p>
  
  <p>DTSTART;TZID=Europe/Brussels:20150318T083000
  DTEND;TZID=Europe/Brussels:20150318T090000</p>
  
  <p>This shows correctly in my calendar, from 08:30 till 09:00</p>
  
  <p>DTSTART;TZID=Europe/Brussels:20150407T083000
  DTEND;TZID=Europe/Brussels:20150407T090000</p>
  
  <p>This is my problem, this shows incorrectly in my calendar: from 09:30 till 10:30.</p>
  
  <p>How can I fix this?</p>