title: NSDate - GMT on iPhone
body: <p>I have the following code in a production application which calculates a GMT date from the date the user enters:</p>
  
  <pre><code>NSDate *localDate = pickedDate;
      NSTimeInterval timeZoneOffset = [[NSTimeZone defaultTimeZone] secondsFromGMT]; // You could also use the systemTimeZone method
      NSTimeInterval gmtTimeInterval = [localDate timeIntervalSinceReferenceDate] - timeZoneOffset;
      NSDate *gmtDate = [NSDate dateWithTimeIntervalSinceReferenceDate:gmtTimeInterval];
  </code></pre>
  
  <p>The code was working fine, until the dreaded daylight savings time came into force in the UK last week.</p>
  
  <p>How can I convert the date into GMT whilst taking into account daylight savings?</p>