diff --git a/spec/plainyearmonth.html b/spec/plainyearmonth.html
index 7c32f348d2..80ef22c915 100644
--- a/spec/plainyearmonth.html
+++ b/spec/plainyearmonth.html
@@ -256,13 +256,15 @@ <h1>Temporal.PlainYearMonth.prototype.add ( _temporalDurationLike_ [ , _options_
         1. Set _options_ to ? GetOptionsObject(_options_).
         1. Let _calendar_ be _yearMonth_.[[Calendar]].
         1. Let _fieldNames_ be ? CalendarFields(_calendar_, « *"monthCode"*, *"year"* »).
+        1. Let _fields_ be ? PrepareTemporalFields(_yearMonth_, _fieldNames_, «»).
         1. Let _sign_ be ! DurationSign(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
         1. If _sign_ &lt; 0, then
           1. Let _dayFromCalendar_ be ? CalendarDaysInMonth(_calendar_, _yearMonth_).
           1. Let _day_ be ? ToPositiveInteger(_dayFromCalendar_).
         1. Else,
           1. Let _day_ be 1.
-        1. Let _date_ be ? CreateTemporalDate(_yearMonth_.[[ISOYear]], _yearMonth_.[[ISOMonth]], _day_, _calendar_).
+        1. Perform ! CreateDataPropertyOrThrow(_fields_, *"day"*, _day_).
+        1. Let _date_ be ? DateFromFields(_calendar_, _fields_, *undefined*).
         1. Let _durationToAdd_ be ! CreateTemporalDuration(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
         1. Let _optionsCopy_ be OrdinaryObjectCreate(%Object.prototype%).
         1. Let _entries_ be ? EnumerableOwnPropertyNames(_options_, ~key+value~).
@@ -289,13 +291,15 @@ <h1>Temporal.PlainYearMonth.prototype.subtract ( _temporalDurationLike_ [ , _opt
         1. Set _options_ to ? GetOptionsObject(_options_).
         1. Let _calendar_ be _yearMonth_.[[Calendar]].
         1. Let _fieldNames_ be ? CalendarFields(_calendar_, « *"monthCode"*, *"year"* »).
+        1. Let _fields_ be ? PrepareTemporalFields(_yearMonth_, _fieldNames_, «»).
         1. Let _sign_ be ! DurationSign(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
         1. If _sign_ &lt; 0, then
           1. Let _dayFromCalendar_ be ? CalendarDaysInMonth(_calendar_, _yearMonth_).
           1. Let _day_ be ? ToPositiveInteger(_dayFromCalendar_).
         1. Else,
           1. Let _day_ be 1.
-        1. Let _date_ be ? CreateTemporalDate(_yearMonth_.[[ISOYear]], _yearMonth_.[[ISOMonth]], _day_, _calendar_).
+        1. Perform ! CreateDataPropertyOrThrow(_fields_, *"day"*, _day_).
+        1. Let _date_ be ? DateFromFields(_calendar_, _fields_, *undefined*).
         1. Let _durationToAdd_ be ! CreateTemporalDuration(_duration_.[[Years]], _duration_.[[Months]], _duration_.[[Weeks]], _balanceResult_.[[Days]], 0, 0, 0, 0, 0, 0).
         1. Let _optionsCopy_ be OrdinaryObjectCreate(%Object.prototype%).
         1. Let _entries_ be ? EnumerableOwnPropertyNames(_options_, ~key+value~).