Editorial: Remove ToISODayOfWeek

ECMA-262 already has a WeekDay equation. We had used some handwavy text in ToISODayOfWeek about "the day of week according to ISO-8601" but this change uses the logic already present in the spec. See: #1641
tc39 · May 6, 2022 · 2d1aae4 · 2d1aae4
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diff --git a/spec/calendar.html b/spec/calendar.html
@@ -452,18 +452,6 @@ <h1>ISODaysInMonth ( _year_, _month_ )</h1>
       </emu-alg>
     </emu-clause>
 
-    <emu-clause id="sec-temporal-toisodayofweek" aoid="ToISODayOfWeek">
-      <h1>ToISODayOfWeek ( _year_, _month_, _day_ )</h1>
-      <emu-alg>
-        1. Assert: _year_ is an integer.
-        1. Assert: _month_ is an integer.
-        1. Assert: _day_ is an integer.
-        1. Let _date_ be the date given by _year_, _month_, and _day_.
-        1. Return _date_'s day of the week according to ISO-8601 as an integer.
-      </emu-alg>
-      <emu-note>Monday is 1 and Sunday is 7.</emu-note>
-    </emu-clause>
-
     <emu-clause id="sec-temporal-toisoweekofyear" aoid="ToISOWeekOfYear">
       <h1>ToISOWeekOfYear ( _year_, _month_, _day_ )</h1>
       <emu-alg>
@@ -959,7 +947,11 @@ <h1>Temporal.Calendar.prototype.dayOfWeek ( _temporalDateLike_ )</h1>
         1. Perform ? RequireInternalSlot(_calendar_, [[InitializedTemporalCalendar]]).
         1. Assert: _calendar_.[[Identifier]] is *"iso8601"*.
         1. Let _temporalDate_ be ? ToTemporalDate(_temporalDateLike_).
-        1. Return 𝔽(! ToISODayOfWeek(_temporalDate_.[[ISOYear]], _temporalDate_.[[ISOMonth]], _temporalDate_.[[ISODay]])).
+        1. Let _epochDays_ be MakeDay(𝔽(_temporalDate_.[[ISOYear]]), 𝔽(_temporalDate_.[[ISOMonth]] - 1), 𝔽(_temporalDate_.[[ISODay]])).
+        1. Assert: _epochDays_ is finite.
+        1. Let _dayOfWeek_ be WeekDay(MakeDate(_epochDays_, *+0*<sub>𝔽</sub>)).
+        1. If _dayOfWeek_ = *+0*<sub>𝔽</sub>, return *7*<sub>𝔽</sub>.
+        1. Return _dayOfWeek_.
       </emu-alg>
     </emu-clause>
 

diff --git a/spec/intl.html b/spec/intl.html
@@ -1852,9 +1852,12 @@ <h1>Temporal.Calendar.prototype.dayOfWeek ( _dateOrDateTime_ )</h1>
             1. Perform ? RequireInternalSlot(_calendar_, [[InitializedTemporalCalendar]]).
             1. Let _temporalDate_ be ? ToTemporalDate(_temporalDateLike_).
             1. If _calendar_.[[Identifier]] is *"iso8601"*, then
-              1. Let _dayOfWeek_ be ! ToISODayOfWeek(_temporalDate_.[[ISOYear]], _temporalDate_.[[ISOMonth]], _temporalDate_.[[ISODay]]).
-            1. Else,
-              1. Let _dayOfWeek_ be ! CalendarDateDayOfWeek(_calendar_.[[Identifier]], _temporalDate_).
+              1. Let _epochDays_ be MakeDay(𝔽(_temporalDate_.[[ISOYear]]), 𝔽(_temporalDate_.[[ISOMonth]] - 1), 𝔽(_temporalDate_.[[ISODay]])).
+              1. Assert: _epochDays_ is finite.
+              1. Let _dayOfWeek_ be WeekDay(MakeDate(_epochDays_, *+0*<sub>𝔽</sub>)).
+              1. If _dayOfWeek_ = *+0*<sub>𝔽</sub>, return *7*<sub>𝔽</sub>.
+              1. Return _dayOfWeek_.
+            1. Let _dayOfWeek_ be ! CalendarDateDayOfWeek(_calendar_.[[Identifier]], _temporalDate_).
             1. Return 𝔽(_dayOfWeek_).
           </emu-alg>
         </emu-clause>