endar_ be _plainDate_.[[Calendar]].
        1. Let _fields_ be ISODateToFields(_calendar_, _plainDate_.[[ISODate]], ~date~).
        1. Let _isoDate_ be ? CalendarYearMonthFromFields(_calendar_, _fields_, ~constrain~).
        1. Return ! CreateTemporalYearMonth(_isoDate_, _calendar_).
        1. NOTE: The call to CalendarYearMonthFromFields is necessary in order to create a PlainYearMonth object with the [[Day]] field of the [[ISODate]] internal slot set correctly.
      </emu-alg>
    </emu-clause>

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