_).
        1. If _weeks_ is not 0 or _days_ is not 0, then
          1. Let _regulatedDate_ be ! RegulateISODate(_yearMonth_.[[Year]], _yearMonth_.[[Month]], _baseDate_.[[Day]], ~constrain~).
          1. Let _balancedDate_ be BalanceISODate(_regulatedDate_.[[Year]], _regulatedDate_.[[Month]], _regulatedDate_.[[Day]] + 7 * _weeks_ + _days_).
          1. Let _y1_ be _balancedDate_.[[Year]].
          1. Let _m1_ be _balancedDate_.[[Month]].
          1. Let _d1_ be _balancedDate_.[[Day]].
        1. Else,
