code: public static final Long date2utc(Date date) {
  
          // use null for a null date
          if (date == null) return null;
          
          long time = date.getTime();
          
          // remove the timezone offset        
          time -= timezoneOffsetMillis(date);
          
          return time;
      }
docs: Converts a gwt Date in the timezone of the current browser to a time in
  UTC.
  
  @return A Long corresponding to the number of milliseconds since January
  1, 1970, 00:00:00 GMT or null if the specified Date is null.