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Aug 14, 2025
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Editorial: Add and use additional MonthCode AOs #73

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Add and use additional MonthCode AOs
sffc Aug 13, 2025
104ebcf
Use variable name "_arithmeticYear_"
sffc Aug 13, 2025
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Address some feedback
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10 changes: 10 additions & 0 deletions biblio.json
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,16 @@
"type": "op",
"aoid": "ZeroDateDuration",
"id": "sec-temporal-zerodateduration"
},
{
"type": "op",
"aoid": "ParseMonthCode",
"id": "sec-temporal-parsemonthcode"
},
{
"type": "op",
"aoid": "CreateMonthCode",
"id": "sec-temporal-createmonthcode"
}
]
}
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135 changes: 121 additions & 14 deletions spec.emu
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Expand Up @@ -533,36 +533,135 @@ contributors: Google, Ecma International
<tr>
<th>Calendar</th>
<th>Additional Month Codes</th>
<th>Leap to Common Month Transformation</th>
</tr>
</thead>
<tr>
<td>*"chinese"*</td>
<td>*"M01L"*, *"M02L"*, *"M03L"*, *"M04L"*, *"M05L"*, *"M06L"*, *"M07L"*, *"M08L"*, *"M09L"*, *"M10L"*, *"M11L"*, *"M12L"*</td>
<td>~skip-backward~</td>
</tr>
<tr>
<td>*"coptic"*</td>
<td>*"M13"*</td>
<td></td>
</tr>
<tr>
<td>*"dangi"*</td>
<td>*"M01L"*, *"M02L"*, *"M03L"*, *"M04L"*, *"M05L"*, *"M06L"*, *"M07L"*, *"M08L"*, *"M09L"*, *"M10L"*, *"M11L"*, *"M12L"*</td>
<td>~skip-backward~</td>
</tr>
<tr>
<td>*"ethioaa"*</td>
<td>*"M13"*</td>
<td></td>
</tr>
<tr>
<td>*"ethiopic"*</td>
<td>*"M13"*</td>
<td></td>
</tr>
<tr>
<td>*"hebrew"*</td>
<td>*"M05L"*</td>
<td>~skip-forward~</td>
</tr>
</table>
</emu-table>
</emu-clause>

<emu-clause id="sec-temporal-yearcontainsmonthcode" type="implementation-defined abstract operation">
<h1>
YearContainsMonthCode (
_calendar_: a calendar type that is not *"iso8601"*,
_arithmeticYear_: an integer,
_monthCode_: a String,
): a Boolean
</h1>
<dl class="header">
<dt>description</dt>
<dd>
It returns whether the given _monthCode_ exists in _arithmeticYear_ of _calendar_.
</dd>
</dl>
<p>It performs the following steps when called:</p>
<emu-alg>
1. Assert: IsValidMonthCodeForCalendar(_calendar_, _monthCode_) is *true*.
1. If ParseMonthCode(_monthCode_).[[IsLeap]] is *false*, return *true*.
1. Return whether the leap month indicated by _monthCode_ exists in the year _arithmeticYear_ in _calendar_, using calendar-dependent behaviour.
</emu-alg>
</emu-clause>

<emu-clause id="sec-temporal-constrainmonthcode" type="abstract operation">
<h1>
ConstrainMonthCode (
_calendar_: a calendar type that is not *"iso8601"*,
_arithmeticYear_: an integer,
_monthCode_: a month code,
_overflow_: ~constrain~ or ~reject~,
): either a normal completion containing a month code or a throw completion
</h1>
<dl class="header">
<dt>description</dt>
<dd>
It returns the month code in _arithmeticYear_ of _calendar_ that best matches the given _monthCode_. If _monthCode_ does not exist in _arithmeticYear_, it is constrained to the best common month if _overflow_ is ~constrain~, or an error is thrown if _overflow_ is ~reject~.
</dd>
</dl>
<p>It performs the following steps when called:</p>
<emu-alg>
1. Assert: IsValidMonthCodeForCalendar(_calendar_, _monthCode_) is *true*.
1. If YearContainsMonthCode(_calendar_, _arithmeticYear_, _monthCode_) is *true*, return _monthCode_.
1. If _overflow_ is ~reject~, throw a *RangeError* exception.
1. Assert: _calendar_ is listed in the Calendar column of <emu-xref href="#table-additional-month-codes"></emu-xref>.
1. Let _r_ be the row in <emu-xref href="#table-additional-month-codes"></emu-xref> which the _calendar_ is in the Calendar column.
1. Let _shiftType_ be the value given in the *"Leap to Common Month Transformation"* column of _r_.
1. If _shiftType_ is ~skip-backward~, then
1. Return CreateMonthCode(ParseMonthCode(_monthCode_).[[MonthNumber]], *false*).
1. Else,
1. Assert: _monthCode_ is *"M05L"*.
1. Return *"M06"*.
</emu-alg>
</emu-clause>

<emu-clause id="sec-temporal-monthcodetoordinal" type="abstract operation">
<h1>
MonthCodeToOrdinal (
_calendar_: a calendar type that is not *"iso8601"*,
_arithmeticYear_: an integer,
_monthCode_: a month code,
): an integer
</h1>
<dl class="header">
<dt>description</dt>
<dd>
It returns the ordinal month number for _monthCode_ in _arithmeticYear_ of _calendar_. The given _monthCode_ must exist in the given year.
</dd>
</dl>
<p>It performs the following steps when called:</p>
<emu-alg>
1. Assert: YearContainsMonthCode(_calendar_, _arithmeticYear_, _monthCode_) is *true*.
1. Let _monthsBefore_ be 0.
1. Let _number_ be 1.
1. Let _isLeap_ be *false*.
1. Let _r_ be the row in <emu-xref href="#table-additional-month-codes"></emu-xref> which the _calendar_ is in the Calendar column.
1. If the *"Leap to Common Month Transformation"* column of _r_ is empty, then
1. Return ParseMonthCode(_monthCode_).[[MonthNumber]].
1. Assert: The *"Additional Month Codes"* column of _r_ does not contain *"M00L"* or *"M13"*.
1. Assert: The following loop will terminate.
1. Repeat, while _number_ &le; 12,
1. Let _currentMonthCode_ be CreateMonthCode(_number_, _isLeap_).
1. If YearContainsMonthCode(_calendar_, _arithmeticYear_, _currentMonthCode_), then
1. Set _monthsBefore_ to _monthsBefore_ + 1.
1. If _currentMonthCode_ is _monthCode_, then
1. Return _monthsBefore_.
1. If _isLeap_ is *false*, then
1. Set _isLeap_ to *true*.
1. Else,
1. Set _isLeap_ to *false*.
1. Set _number_ to _number_ + 1.
</emu-alg>
</emu-clause>

<emu-clause id="sec-temporal-isvaliderayearforcalendar" type="abstract operation">
<h1>
IsValidEraYearForCalendar (
Expand Down Expand Up @@ -903,10 +1002,11 @@ contributors: Google, Ecma International
<p>It performs the following steps when called:</p>
<emu-alg>
1. Let _calendarDate_ be CalendarISOToDate(_calendar_, _isoDate_).
1. Add _duration_.[[Years]] to _calendarDate_.
1. (This step only matters for lunisolar calendars.) If _calendarDate_.[[MonthCode]] is a leap month that doesn't exist in the year, then:
1. Set _calendarDate_ to another date according to the cultural conventions of that calendar's users. Of the currently supported calendars: if _calendar_ is *"chinese"* or *"dangi"*, change _calendarDate_.[[MonthCode]] to the same month code but without the *"L"*. If _calendar_ is *"hebrew"*, change _calendarDate_.[[MonthCode]] from *"M05L"* to *"M06"*.
1. Update _calendarDate_.[[Month]] accordingly.
1. Add _duration_.[[Years]] to _calendarDate_ without changing any less-significant fields.
1. If YearContainsMonthCode(_calendar_, _calendarDate_.[[Year]], _calendarDate_.[[MonthCode]]) is *false*, then
1. NOTE: This only happens in lunisolar calendars.
1. Set _calendarDate_.[[MonthCode]] to ! ConstrainMonthCode(_calendar_, _calendarDate_.[[Year]], _calendarDate_.[[MonthCode]], ~constrain~).
1. Set _calendarDate_.[[Month]] to MonthCodeToOrdinal(_calendar_, _calendarDate_.[[Year]], _calendarDate_.[[MonthCode]]).
1. Add _duration_.[[Months]] to _calendarDate_, balancing _calendarDate_ if it goes over a year boundary.
1. If the date described by _calendarDate_ does not exist, then
1. If _overflow_ is ~reject~, throw a *RangeError* exception.
Expand Down Expand Up @@ -972,16 +1072,23 @@ contributors: Google, Ecma International
<p>This definition supersedes the definition provided in <emu-xref href="#sec-temporal-nonisocalendardatetoiso"></emu-xref>.</p>
<p>It performs the following steps when called:</p>
<emu-alg>
1. If _fields_.[[Era]] and _fields_.[[EraYear]] are not ~unset~ and IsValidEraYearForCalendar(_calendar_, _fields_.[[Era]], _fields_.[[EraYear]]) is *false*, throw a *RangeError* exception.
1. If _fields_.[[MonthCode]] is not ~unset~ and IsValidMonthCodeForCalendar(_calendar_, _fields_.[[MonthCode]]) is *false*, throw a *RangeError* exception.
1. If _fields_ describes an existing date in _calendar_, return an implementation-defined ISO Date Record that corresponds to the date described by _fields_.
1. If _overflow_ is ~reject~, throw a *RangeError* exception.
1. (This step only matters for lunisolar calendars.) If _fields_.[[MonthCode]] is a leap month that doesn't exist in the year, then:
1. Set _fields_ to another date according to the cultural conventions of that calendar's users. Of the currently supported calendars: if _calendar_ is *"chinese"* or *"dangi"*, change _fields_.[[MonthCode]] to the same month code but without the *"L"*. If _calendar_ is *"hebrew"*, change _fields_.[[MonthCode]] from *"M05L"* to *"M06"*.
1. Update _fields_.[[Month]] accordingly.
1. If _fields_.[[MonthCode]] is a valid month code for _fields_.[[Year]], but the date described by _fields_ does not exist, set _fields_.[[Day]] to the closest day in the same month. If there are two equally-close dates in the same month, pick the later one.
1. (This step does not apply to any currently supported calendars.) If the date described by _fields_ still does not exist, set _fields_ to the closest date in the same year. If there are two equally-close dates in that year, pick the later one.
1. Return an implementation-defined ISO Date Record that corresponds to the date described by _fields_.
1. If _fields_.[[Era]] and _fields_.[[EraYear]] are not ~unset~, then
1. If IsValidEraYearForCalendar(_calendar_, _fields_.[[Era]], _fields_.[[EraYear]]) is *false*, throw a *RangeError* exception.
1. Let _arithmeticYear_ be CalendarDateArithmeticYearForEraYear(_calendar_, _fields_.[[Era]], _fields_.[[EraYear]]).
1. Else,
1. Assert: _fields_.[[Year]] is not ~unset~.
1. Let _arithmeticYear_ be _fields_.[[Year]].
1. If _fields_.[[MonthCode]] is not ~unset~, then
1. If IsValidMonthCodeForCalendar(_calendar_, _fields_.[[MonthCode]]) is *false*, throw a *RangeError* exception.
1. Let _constrainedMonthCode_ be ? ConstrainMonthCode(_calendar_, _arithmeticYear_, _fields_.[[MonthCode]], _overflow_).
1. Let _ordinalMonth_ be MonthCodeToOrdinal(_calendar_, _arithmeticYear_, _constrainedMonthCode_).
1. Else,
1. Assert: _fields_.[[Month]] is not ~unset~.
1. Let _ordinalMonth_ be _fields_.[[Month]].
1. Let _day_ be _fields_.[[Day]].
1. Assert: _day_ is not ~unset~.
1. If the date described by _calendar_, _arithmeticYear_, _ordinalMonth_, and _day_ does not exist, set _day_ to the closest day in the same month. If there are two equally-close dates in the same month, pick the later one.
1. Return an implementation-defined ISO Date Record that corresponds to the date described by _calendar_, _arithmeticYear_, _ordinalMonth_, and _day_.
</emu-alg>
</emu-clause>

Expand Down