title: Get TimeZone offset value from TimeZone without TimeZone name
body: <p>I need to save the phone's timezone in the format [+/-]hh:mm</p>
  
  <p>I am using TimeZone class to deal with this, but the only format I can get is the following:</p>
  
  <pre><code>PST -05:00
  GMT +02:00
  </code></pre>
  
  <p>I would rather not substring the result, is there any key or option flag I can set to only get the value and not the name of that timezone (GMT/CET/PST...)?</p>