title: Date.getTimezoneOffset inverted?
body: <p>I have a JSON response from my server giving me UTC Unix timestamps in seconds.  I'm parsing that into JavaScript dates that will be used in a chart (displaying the time in the user's locale).</p>
  
  <p>I obviously have to coax the timestamp I have (in UTC) into the browser's locale, so I wrote a function that creates a new <code>Date</code> in the browser's locale, calls <code>getTimezoneOffset()</code> on it to get the "offset in minutes" in the current locale, as per <a href="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date" rel="noreferrer">the MDN</a>, converts both to milliseconds, and returns the sum.  Now I have a JavaScript friendly Unix timestamp in the user's locale.</p>
  
  <p>However, I don't.</p>
  
  <p>as it turns out, <code>(new Date()).getTimezoneOffset()</code> returns (positive) 300 in GMT-5 and -120 in GMT+2.  Why is the offset inverted?  I would have expected the offset to match the sign of the timezone - ie: I need to subtract 300 minutes to get to GMT-5, and ADD 120 minutes to get to GMT+2.  Instead, I have to subtract the values that are returned by <code>getTimezoneOffset</code></p>