ms the following steps when called:</p>
      <emu-alg>
        1. Let _plainDate_ be the *this* value.
        1. Perform ? RequireInternalSlot(_plainDate_, [[InitializedTemporalDate]]).
        1. If ? IsPartialTemporalObject(_temporalDateLike_) is *false*, throw a *TypeError* exception.
        1. Let _calendar_ be _plainDate_.[[Calendar]].
        1. Let _fields_ be ISODateToFields(_calendar_, _plainDate_.[[ISODate]], ~date~).
        1. Let _partialDate_ be ? PrepareCalendarFields(_calendar_, _temporal