Editorial: Replace BalanceISODateTime with subtraction

Author: anba

spec/instant.html

@@ -413,9 +413,10 @@ <h1>
         1. Assert: Either _parsed_.[[TimeZone]].[[OffsetString]] is not ~empty~ or _parsed_.[[TimeZone]].[[Z]] is *true*, but not both.
         1. If _parsed_.[[TimeZone]].[[Z]] is *true*, let _offsetNanoseconds_ be 0; otherwise, let _offsetNanoseconds_ be ! ParseDateTimeUTCOffset(_parsed_.[[TimeZone]].[[OffsetString]]).
         1. If _parsed_.[[Time]] is ~start-of-day~, let _time_ be MidnightTimeRecord(); else let _time_ be _parsed_.[[Time]].
-        1. Let _balanced_ be BalanceISODateTime(_parsed_.[[Year]], _parsed_.[[Month]], _parsed_.[[Day]], _time_.[[Hour]], _time_.[[Minute]], _time_.[[Second]], _time_.[[Millisecond]], _time_.[[Microsecond]], _time_.[[Nanosecond]] - _offsetNanoseconds_).
-        1. Perform ? CheckISODaysRange(_balanced_.[[ISODate]]).
-        1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_).
+        1. Let _isoDate_ be CreateISODateRecord(_parsed_.[[Year]], _parsed_.[[Month]], _parsed_.[[Day]]).
+        1. Let _isoDateTime_ be CombineISODateAndTimeRecord(_isoDate_, _time_).
+        1. Perform ? CheckISODaysRange(_isoDate_).
+        1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_isoDateTime_) - _offsetNanoseconds_.
         1. If IsValidEpochNanoseconds(_epochNanoseconds_) is *false*, throw a *RangeError* exception.
         1. Return ! CreateTemporalInstant(_epochNanoseconds_).
       </emu-alg>

spec/timezone.html

@@ -349,9 +349,9 @@ <h1>
       <emu-alg>
         1. Let _parseResult_ be ! ParseTimeZoneIdentifier(_timeZone_).
         1. If _parseResult_.[[OffsetMinutes]] is not ~empty~, then
-          1. Let _balanced_ be BalanceISODateTime(_isoDateTime_.[[ISODate]].[[Year]], _isoDateTime_.[[ISODate]].[[Month]], _isoDateTime_.[[ISODate]].[[Day]], _isoDateTime_.[[Time]].[[Hour]], _isoDateTime_.[[Time]].[[Minute]] - _parseResult_.[[OffsetMinutes]], _isoDateTime_.[[Time]].[[Second]], _isoDateTime_.[[Time]].[[Millisecond]], _isoDateTime_.[[Time]].[[Microsecond]], _isoDateTime_.[[Time]].[[Nanosecond]]).
-          1. Perform ? CheckISODaysRange(_balanced_.[[ISODate]]).
-          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_).
+          1. Let _offsetNanoseconds_ be _parseResult_.[[OffsetMinutes]] × 6 × 10<sup>10</sup>.
+          1. Perform ? CheckISODaysRange(_isoDateTime_.[[ISODate]]).
+          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_isoDateTime_) - _offsetNanoseconds_.
           1. Let _possibleEpochNanoseconds_ be « _epochNanoseconds_ ».
         1. Else,
           1. Perform ? CheckISODaysRange(_isoDateTime_.[[ISODate]]).

spec/zoneddatetime.html

@@ -915,9 +915,8 @@ <h1>
         1. If _offsetBehaviour_ is ~wall~, or _offsetBehaviour_ is ~option~ and _offsetOption_ is ~ignore~, then
           1. Return ? GetEpochNanosecondsFor(_timeZone_, _isoDateTime_, _disambiguation_).
         1. If _offsetBehaviour_ is ~exact~, or _offsetBehaviour_ is ~option~ and _offsetOption_ is ~use~, then
-          1. Let _balanced_ be BalanceISODateTime(_isoDate_.[[Year]], _isoDate_.[[Month]], _isoDate_.[[Day]], _time_.[[Hour]], _time_.[[Minute]], _time_.[[Second]], _time_.[[Millisecond]], _time_.[[Microsecond]], _time_.[[Nanosecond]] - _offsetNanoseconds_).
-          1. Perform ? CheckISODaysRange(_balanced_.[[ISODate]]).
-          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_balanced_).
+          1. Perform ? CheckISODaysRange(_isoDate_).
+          1. Let _epochNanoseconds_ be GetUTCEpochNanoseconds(_isoDateTime_) - _offsetNanoseconds_.
           1. If IsValidEpochNanoseconds(_epochNanoseconds_) is *false*, throw a *RangeError* exception.
           1. Return _epochNanoseconds_.
         1. Assert: _offsetBehaviour_ is ~option~.