Editorial: rename TimeZone "nanoseconds" slot/AOs

Now that we've limited TimeZone's [[OffsetNanoseconds]] internal slot
to minute precision, this commit refactors TimeZone to clarify that only
minutes are allowed in that slot and related abstract operations.

Changes:
* Renames TimeZone's [[OffsetNanoseconds]] internal slot to
  [[OffsetMinutes]]
* Changes ParseTimeZoneIdentifier to return an [[OffsetMinutes]] field
  instead of an [[OffsetNanoseconds]] field.
* Changes FormatOffsetTimeZoneIdentifier to expect a minutes argument.

The goal of this change is to avoid the complexity and potential
confusion from a slot and AOs that deal with "nanoseconds" values
that nonetheless are restricted to minutes.

polyfill/lib/ecmascript.mjs

@@ -560,7 +560,7 @@ export function ParseTimeZoneIdentifier(identifier) {
   if (OFFSET_IDENTIFIER.test(identifier)) {
     // The regex limits the input to minutes precision
     const { offsetNanoseconds } = ParseDateTimeUTCOffset(identifier);
-    return { offsetNanoseconds };
+    return { offsetMinutes: offsetNanoseconds / 6e10 };
   }
   return { tzName: identifier };
 }
@@ -2097,8 +2097,8 @@ export function ToTemporalTimeZoneSlotValue(temporalTimeZoneLike) {
   const { tzName, offset, z } = ParseTemporalTimeZoneString(identifier);
   if (tzName) {
     // tzName is any valid identifier string in brackets, and could be an offset identifier
-    const { offsetNanoseconds } = ParseTimeZoneIdentifier(tzName);
-    if (offsetNanoseconds !== undefined) return FormatOffsetTimeZoneIdentifier(offsetNanoseconds);
+    const { offsetMinutes } = ParseTimeZoneIdentifier(tzName);
+    if (offsetMinutes !== undefined) return FormatOffsetTimeZoneIdentifier(offsetMinutes);
 
     const record = GetAvailableNamedTimeZoneIdentifier(tzName);
     if (!record) throw new RangeError(`Unrecognized time zone ${tzName}`);
@@ -2110,7 +2110,7 @@ export function ToTemporalTimeZoneSlotValue(temporalTimeZoneLike) {
   if (hasSubMinutePrecision) {
     throw new RangeError(`Seconds not allowed in offset time zone: ${offset}`);
   }
-  return FormatOffsetTimeZoneIdentifier(offsetNanoseconds);
+  return FormatOffsetTimeZoneIdentifier(offsetNanoseconds / 6e10);
 }
 
 export function ToTemporalTimeZoneIdentifier(slotValue) {
@@ -2180,7 +2180,7 @@ export function GetOffsetStringFor(timeZone, instant) {
 // But in the polyfill, we re-use it to provide clearer error messages.
 function formatOffsetStringNanoseconds(offsetNs) {
   const offsetMinutes = MathTrunc(offsetNs / 6e10);
-  let offsetStringMinutes = FormatOffsetTimeZoneIdentifier(offsetMinutes * 6e10);
+  let offsetStringMinutes = FormatOffsetTimeZoneIdentifier(offsetMinutes);
   const subMinuteNanoseconds = MathAbs(offsetNs) % 6e10;
   if (!subMinuteNanoseconds) return offsetStringMinutes;
 
@@ -2736,9 +2736,9 @@ export function GetNamedTimeZoneOffsetNanoseconds(id, epochNanoseconds) {
   return +utc.minus(epochNanoseconds);
 }
 
-export function FormatOffsetTimeZoneIdentifier(offsetNanoseconds) {
-  const sign = offsetNanoseconds < 0 ? '-' : '+';
-  const absoluteMinutes = MathAbs(offsetNanoseconds / 6e10);
+export function FormatOffsetTimeZoneIdentifier(offsetMinutes) {
+  const sign = offsetMinutes < 0 ? '-' : '+';
+  const absoluteMinutes = MathAbs(offsetMinutes);
   const intHours = MathFloor(absoluteMinutes / 60);
   const hh = ISODateTimePartString(intHours);
   const intMinutes = absoluteMinutes % 60;
@@ -2748,7 +2748,7 @@ export function FormatOffsetTimeZoneIdentifier(offsetNanoseconds) {
 
 export function FormatDateTimeUTCOffsetRounded(offsetNanoseconds) {
   offsetNanoseconds = RoundNumberToIncrement(bigInt(offsetNanoseconds), 60e9, 'halfExpand').toJSNumber();
-  return FormatOffsetTimeZoneIdentifier(offsetNanoseconds);
+  return FormatOffsetTimeZoneIdentifier(offsetNanoseconds / 6e10);
 }
 
 export function GetUTCEpochNanoseconds(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond) {

polyfill/lib/timezone.mjs

@@ -28,8 +28,8 @@ export class TimeZone {
     }
     let stringIdentifier = ES.ToString(identifier);
     const parseResult = ES.ParseTimeZoneIdentifier(identifier);
-    if (parseResult.offsetNanoseconds !== undefined) {
-      stringIdentifier = ES.FormatOffsetTimeZoneIdentifier(parseResult.offsetNanoseconds);
+    if (parseResult.offsetMinutes !== undefined) {
+      stringIdentifier = ES.FormatOffsetTimeZoneIdentifier(parseResult.offsetMinutes);
     } else {
       const record = ES.GetAvailableNamedTimeZoneIdentifier(stringIdentifier);
       if (!record) throw new RangeError(`Invalid time zone identifier: ${stringIdentifier}`);
@@ -56,8 +56,8 @@ export class TimeZone {
     instant = ES.ToTemporalInstant(instant);
     const id = GetSlot(this, TIMEZONE_ID);
 
-    const offsetNanoseconds = ES.ParseTimeZoneIdentifier(id).offsetNanoseconds;
-    if (offsetNanoseconds !== undefined) return offsetNanoseconds;
+    const offsetMinutes = ES.ParseTimeZoneIdentifier(id).offsetMinutes;
+    if (offsetMinutes !== undefined) return offsetMinutes * 6e10;
 
     return ES.GetNamedTimeZoneOffsetNanoseconds(id, GetSlot(instant, EPOCHNANOSECONDS));
   }
@@ -85,8 +85,8 @@ export class TimeZone {
     const Instant = GetIntrinsic('%Temporal.Instant%');
     const id = GetSlot(this, TIMEZONE_ID);
 
-    const offsetNanoseconds = ES.ParseTimeZoneIdentifier(id).offsetNanoseconds;
-    if (offsetNanoseconds !== undefined) {
+    const offsetMinutes = ES.ParseTimeZoneIdentifier(id).offsetMinutes;
+    if (offsetMinutes !== undefined) {
       const epochNs = ES.GetUTCEpochNanoseconds(
         GetSlot(dateTime, ISO_YEAR),
         GetSlot(dateTime, ISO_MONTH),
@@ -99,7 +99,7 @@ export class TimeZone {
         GetSlot(dateTime, ISO_NANOSECOND)
       );
       if (epochNs === null) throw new RangeError('DateTime outside of supported range');
-      return [new Instant(epochNs.minus(offsetNanoseconds))];
+      return [new Instant(epochNs.minus(offsetMinutes * 6e10))];
     }
 
     const possibleEpochNs = ES.GetNamedTimeZoneEpochNanoseconds(

spec/intl.html

@@ -2543,7 +2543,7 @@ <h1>Temporal.ZonedDateTime.prototype.toLocaleString ( [ _locales_ [ , _options_
             1. Let _dateTimeFormat_ be ! OrdinaryCreateFromConstructor(%DateTimeFormat%, %DateTimeFormat.prototype%, « [[InitializedDateTimeFormat]], [[Locale]], [[Calendar]], [[NumberingSystem]], [[TimeZone]], [[Weekday]], [[Era]], [[Year]], [[Month]], [[Day]], [[DayPeriod]], [[Hour]], [[Minute]], [[Second]], [[FractionalSecondDigits]], [[TimeZoneName]], [[HourCycle]], [[Pattern]], [[BoundFormat]] »).
             1. Let _timeZone_ be ? ToTemporalTimeZoneIdentifier(_zonedDateTime_.[[TimeZone]]).
             1. Let _timeZoneParseResult_ be ? ParseTimeZoneIdentifier(_timeZone_).
-            1. If _timeZoneParseResult_.[[OffsetNanoseconds]] is not ~empty~, throw a *RangeError* exception.
+            1. If _timeZoneParseResult_.[[OffsetMinutes]] is not ~empty~, throw a *RangeError* exception.
             1. Let _timeZoneIdentifierRecord_ be GetAvailableNamedTimeZoneIdentifier(_timeZone_).
             1. If _timeZoneIdentifierRecord_ is ~empty~, throw a *RangeError* exception.
             1. Set _timeZone_ to _timeZoneIdentifierRecord_.[[PrimaryIdentifier]].

spec/mainadditions.html

@@ -350,8 +350,8 @@ <h1>
       <emu-alg>
         1. Let _systemTimeZoneIdentifier_ be SystemTimeZoneIdentifier().
         1. <ins>Let _parseResult_ be ! ParseTimeZoneIdentifier(_systemTimeZoneIdentifier_).</ins>
-        1. If <del>IsTimeZoneOffsetString(_systemTimeZoneIdentifier_) is *true*</del><ins>_parseResult_.[[OffsetNanoseconds]] is not ~empty~</ins>, then
-          1. Let _offsetNs_ be <del>ParseTimeZoneOffsetString(_systemTimeZoneIdentifier_)</del><ins>_parseResult_.[[OffsetNanoseconds]]</ins>.
+        1. If <del>IsTimeZoneOffsetString(_systemTimeZoneIdentifier_) is *true*</del><ins>_parseResult_.[[OffsetMinutes]] is not ~empty~</ins>, then
+          1. Let _offsetNs_ be <del>ParseTimeZoneOffsetString(_systemTimeZoneIdentifier_)</del><ins>_parseResult_.[[OffsetMinutes]] × (6 × 10<sup>10</sup>)</ins>.
         1. Else,
           1. Let _offsetNs_ be GetNamedTimeZoneOffsetNanoseconds(_systemTimeZoneIdentifier_, ℤ(ℝ(_t_) × 10<sup>6</sup>)).
         1. Let _offsetMs_ be truncate(_offsetNs_ / 10<sup>6</sup>).
@@ -385,8 +385,8 @@ <h1>
       <emu-alg>
         1. Let _systemTimeZoneIdentifier_ be SystemTimeZoneIdentifier().
         1. <ins>Let _parseResult_ be ! ParseTimeZoneIdentifier(_systemTimeZoneIdentifier_).</ins>
-        1. If <del>IsTimeZoneOffsetString(_systemTimeZoneIdentifier_) is *true*</del><ins>_parseResult_.[[OffsetNanoseconds]] is not ~empty~</ins>, then
-          1. Let _offsetNs_ be <del>ParseTimeZoneOffsetString(_systemTimeZoneIdentifier_)</del><ins>_parseResult_.[[OffsetNanoseconds]]</ins>.
+        1. If <del>IsTimeZoneOffsetString(_systemTimeZoneIdentifier_) is *true*</del><ins>_parseResult_.[[OffsetMinutes]] is not ~empty~</ins>, then
+          1. Let _offsetNs_ be <del>ParseTimeZoneOffsetString(_systemTimeZoneIdentifier_)</del><ins>_parseResult_.[[OffsetMinutes]] × (6 × 10<sup>10</sup>)</ins>.
         1. Else,
           1. Let _possibleInstants_ be GetNamedTimeZoneEpochNanoseconds(_systemTimeZoneIdentifier_, ℝ(YearFromTime(_t_)), ℝ(MonthFromTime(_t_)) + 1, ℝ(DateFromTime(_t_)), ℝ(HourFromTime(_t_)), ℝ(MinFromTime(_t_)), ℝ(SecFromTime(_t_)), ℝ(msFromTime(_t_)), 0, 0).
           1. NOTE: The following steps ensure that when _t_ represents local time repeating multiple times at a negative time zone transition (e.g. when the daylight saving time ends or the time zone offset is decreased due to a time zone rule change) or skipped local time at a positive time zone transition (e.g. when the daylight saving time starts or the time zone offset is increased due to a time zone rule change), _t_ is interpreted using the time zone offset before the transition.
@@ -436,8 +436,8 @@ <h1>
       <emu-alg>
         1. Let _systemTimeZoneIdentifier_ be SystemTimeZoneIdentifier().
         1. <ins>Let _parseResult_ be ! ParseTimeZoneIdentifier(_systemTimeZoneIdentifier_).</ins>
-        1. If <del>IsTimeZoneOffsetString(_systemTimeZoneIdentifier_) is *true*</del><ins>_parseResult_.[[OffsetNanoseconds]] is not ~empty~</ins>, then
-          1. Let _offsetNs_ be <del>ParseTimeZoneOffsetString(_systemTimeZoneIdentifier_)</del><ins>_parseResult_.[[OffsetNanoseconds]]</ins>.
+        1. If <del>IsTimeZoneOffsetString(_systemTimeZoneIdentifier_) is *true*</del><ins>_parseResult_.[[OffsetMinutes]] is not ~empty~</ins>, then
+          1. Let _offsetNs_ be <del>ParseTimeZoneOffsetString(_systemTimeZoneIdentifier_)</del><ins>_parseResult_.[[OffsetMinutes]] × (6 × 10<sup>10</sup>)</ins>.
         1. Else,
           1. Let _offsetNs_ be GetNamedTimeZoneOffsetNanoseconds(_systemTimeZoneIdentifier_, ℤ(ℝ(_tv_) × 10<sup>6</sup>)).
         1. <del>Let _offset_ be 𝔽(truncate(_offsetNs_ / 10<sup>6</sup>)).</del>