}

      // Convert two-digit years into four-digit years. 99 becomes 1999, 15 becomes 2015.
      if (year in 70..99) year += 1900
      if (year in 0..69) year += 2000

      // If any partial is omitted or out of range, return -1. The date is impossible. Note that leap
      // seconds are not supported by this syntax.
      require(year >= 1601)
      require(month != -1)