code: public static final Date utc2date(Long time) {
  
          // don't accept negative values
          if (time == null || time < 0) return null;
          
          // add the timezone offset
          time += timezoneOffsetMillis(new Date(time));
  
          return new Date(time);
      }
docs: Converts a time in UTC to a gwt Date object which is in the timezone of
  the current browser.
  
  @return The Date corresponding to the time, adjusted for the timezone of
  the current browser. null if the specified time is null or
  represents a negative number.