code: @GwtIncompatible("incompatible method")
      public static Calendar toCalendar(final Date date, final TimeZone tz) {
          final Calendar c = Calendar.getInstance(tz);
          c.setTime(date);
          return c;
      }
docs: Converts a {@code Date} of a given {@code TimeZone} into a {@code Calendar}
  @param date the date to convert to a Calendar
  @param tz the time zone of the {@code date}
  @return the created Calendar
  @throws NullPointerException if {@code date} or {@code tz} is null