Implement default calendar option 1

This implements "option 1" for the default calendar, which is defaulting
to the full ISO 8601 calendar everywhere. We add optional calendar
parameters to Temporal.Absolute.prototype.inTimeZone, Temporal.now.date,
Temporal.now.dateTime, and Temporal.TimeZone.prototype.getDateTimeFor.

See: #292.

docs/absolute.md

@@ -206,16 +206,20 @@ Same as `getEpochSeconds()`, but with nanosecond (10<sup>&minus;9</sup> second)
 
 The value returned from this method is suitable to be passed to `new Temporal.Absolute()`.
 
-### absolute.**inTimeZone**(_timeZone_: Temporal.TimeZone | string) : Temporal.DateTime
+### absolute.**inTimeZone**(_timeZone_: Temporal.TimeZone | string, _calendar_?: Temporal.Calendar | string) : Temporal.DateTime
 
 **Parameters:**
 - `timeZone` (object or string): A `Temporal.TimeZone` object, or a string description of the time zone; either its IANA name or UTC offset.
+- `calendar` (optional object or string): A `Temporal.Calendar` object, or a calendar identifier.
+  The default is to use the ISO 8601 calendar.
 
-**Returns:** a `Temporal.DateTime` object indicating the calendar date and wall-clock time in `timeZone` at the absolute time indicated by `absolute`.
+**Returns:** a `Temporal.DateTime` object indicating the calendar date and wall-clock time in `timeZone`, according to the reckoning of `calendar`, at the absolute time indicated by `absolute`.
 
 For a list of IANA time zone names, see the current version of the [IANA time zone database](https://www.iana.org/time-zones).
 A convenient list is also available [on Wikipedia](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones), although it might not reflect the latest official status.
 
+For a list of calendar identifiers, see the documentation for [Intl.DateTimeFormat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat/DateTimeFormat#Parameters).
+
 This method is one way to convert a `Temporal.Absolute` to a `Temporal.DateTime`.
 
 Example usage:

docs/now.md

@@ -54,16 +54,18 @@ nextTransition.inTimeZone(tz);
 // On 2020-03-08T03:00 the clock will change from UTC -08:00 to -07:00
 ```
 
-### Temporal.now.**dateTime**(_timeZone_: Temporal.TimeZone | string = Temporal.now.timeZone()) : Temporal.DateTime
+### Temporal.now.**dateTime**(_timeZone_: Temporal.TimeZone | string = Temporal.now.timeZone(), _calendar_: Temporal.Calendar | string = 'iso8601') : Temporal.DateTime
 
 **Parameters:**
 - `timeZone` (optional `Temporal.TimeZone` or string): The time zone to get the current date and time in.
   If not given, the current system time zone will be used.
+- `calendar` (optional `Temporal.Calendar` or string): The calendar system to get the current date and time in.
+  If not given, the ISO 8601 calendar will be used.
 
 **Returns:** a `Temporal.DateTime` object representing the current system date and time.
 
 This method gets the current calendar date and wall-clock time according to the system settings.
-Optionally a time zone can be given in which the time is computed.
+Optionally a time zone can be given in which the time is computed, and a calendar system in which the date is reckoned.
 
 Example usage:
 ```js
@@ -83,11 +85,13 @@ Object.entries(financialCentres).forEach(([name, timeZone]) => {
 // Tokyo: 2020-01-25T14:52:14.759534758
 ```
 
-### Temporal.now.**date**(_timeZone_: Temporal.TimeZone | string = Temporal.now.timeZone()) : Temporal.Date
+### Temporal.now.**date**(_timeZone_: Temporal.TimeZone | string = Temporal.now.timeZone(), _calendar_: Temporal.Calendar | string = 'iso8601') : Temporal.Date
 
 **Parameters:**
 - `timeZone` (optional `Temporal.TimeZone` or string): The time zone to get the current date and time in.
   If not given, the current system time zone will be used.
+- `calendar` (optional `Temporal.Calendar` or string): The calendar system to get the current date and time in.
+  If not given, the ISO 8601 calendar will be used.
 
 **Returns:** a `Temporal.Date` object representing the current system date.
 

docs/timezone.md

@@ -164,12 +164,14 @@ tz = new Temporal.TimeZone('-08:00');
 tz.getOffsetStringFor(timestamp);  // => -08:00
 ```
 
-### timeZone.**getDateTimeFor**(_absolute_: Temporal.Absolute) : Temporal.DateTime
+### timeZone.**getDateTimeFor**(_absolute_: Temporal.Absolute, _calendar_?: Temporal.Calendar | string) : Temporal.DateTime
 
 **Parameters:**
 - `absolute` (`Temporal.Absolute`): An absolute time to convert.
+- `calendar` (optional object or string): A `Temporal.Calendar` object, or a calendar identifier.
+  The default is to use the ISO 8601 calendar.
 
-**Returns:** A `Temporal.DateTime` object indicating the calendar date and wall-clock time in `timeZone` at the absolute time indicated by `absolute`.
+**Returns:** A `Temporal.DateTime` object indicating the calendar date and wall-clock time in `timeZone`, according to the reckoning of `calendar`, at the absolute time indicated by `absolute`.
 
 This method is one way to convert a `Temporal.Absolute` to a `Temporal.DateTime`.
 

polyfill/index.d.ts

@@ -204,7 +204,7 @@ export namespace Temporal {
       other: Temporal.Absolute,
       options?: DifferenceOptions<'days' | 'hours' | 'minutes' | 'seconds'>
     ): Temporal.Duration;
-    inTimeZone(tzLike?: Temporal.TimeZone | string): Temporal.DateTime;
+    inTimeZone(tzLike?: Temporal.TimeZone | string, calendar?: Temporal.Calendar | string): Temporal.DateTime;
     toLocaleString(locales?: string | string[], options?: Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(tzLike?: Temporal.TimeZone | string): string;
@@ -541,7 +541,7 @@ export namespace Temporal {
     readonly name: string;
     getOffsetNanosecondsFor(absolute: Temporal.Absolute): number;
     getOffsetStringFor(absolute: Temporal.Absolute): string;
-    getDateTimeFor(absolute: Temporal.Absolute): Temporal.DateTime;
+    getDateTimeFor(absolute: Temporal.Absolute, calendar?: Temporal.Calendar | string): Temporal.DateTime;
     getAbsoluteFor(dateTime: Temporal.DateTime, options?: ToAbsoluteOptions): Temporal.Absolute;
     getTransitions(startingPoint: Temporal.Absolute): IteratorResult<Temporal.Absolute>;
     getPossibleAbsolutesFor(dateTime: Temporal.DateTime): Temporal.Absolute[];
@@ -620,8 +620,13 @@ export namespace Temporal {
      * {@link https://en.wikipedia.org/wiki/List_of_tz_database_time_zones|IANA time zone identifier}
      * string (e.g. `'Europe/London'`) or a `Temporal.TimeZone` instance. If omitted,
      * the environment's current time zone will be used.
+     * @param {Temporal.Calendar | string} [calendar] - calendar identifier or a
+     * `Temporal.Calendar` instance. If omitted, the ISO 8601 calendar is used.
      */
-    export function dateTime(tzLike?: Temporal.TimeZone | string): Temporal.DateTime;
+    export function dateTime(
+      tzLike?: Temporal.TimeZone | string,
+      calendar?: Temporal.Calendar | string
+    ): Temporal.DateTime;
 
     /**
      * Get the current calendar date in a specific time zone.
@@ -630,8 +635,10 @@ export namespace Temporal {
      * {@link https://en.wikipedia.org/wiki/List_of_tz_database_time_zones|IANA time zone identifier}
      * string (e.g. `'Europe/London'`) or a `Temporal.TimeZone` instance. If omitted,
      * the environment's current time zone will be used.
+     * @param {Temporal.Calendar | string} [calendar] - calendar identifier or a
+     * `Temporal.Calendar` instance. If omitted, the ISO 8601 calendar is used.
      */
-    export function date(tzLike?: Temporal.TimeZone | string): Temporal.Date;
+    export function date(tzLike?: Temporal.TimeZone | string, calendar?: Temporal.Calendar | string): Temporal.Date;
 
     /**
      * Get the current clock time in a specific time zone.

polyfill/lib/absolute.mjs

@@ -143,10 +143,10 @@ export class Absolute {
   valueOf() {
     throw new TypeError('use compare() or equals() to compare Temporal.Absolute');
   }
-  inTimeZone(temporalTimeZoneLike = 'UTC') {
+  inTimeZone(temporalTimeZoneLike = 'UTC', calendar = undefined) {
     if (!ES.IsTemporalAbsolute(this)) throw new TypeError('invalid receiver');
     const timeZone = ES.ToTemporalTimeZone(temporalTimeZoneLike);
-    return timeZone.getDateTimeFor(this);
+    return timeZone.getDateTimeFor(this, calendar);
   }
 
   static fromEpochSeconds(epochSeconds) {

polyfill/lib/now.mjs

@@ -13,14 +13,14 @@ function absolute() {
   const Absolute = GetIntrinsic('%Temporal.Absolute%');
   return new Absolute(ES.SystemUTCEpochNanoSeconds());
 }
-function dateTime(temporalTimeZoneLike = timeZone()) {
+function dateTime(temporalTimeZoneLike = timeZone(), calendar = undefined) {
   const timeZone = ES.ToTemporalTimeZone(temporalTimeZoneLike);
   const abs = absolute();
-  const dateTime = timeZone.getDateTimeFor(abs);
+  const dateTime = timeZone.getDateTimeFor(abs, calendar);
   return dateTime;
 }
-function date(temporalTimeZoneLike) {
-  return dateTime(temporalTimeZoneLike).getDate();
+function date(temporalTimeZoneLike, calendar = undefined) {
+  return dateTime(temporalTimeZoneLike, calendar).getDate();
 }
 function time(temporalTimeZoneLike) {
   return dateTime(temporalTimeZoneLike).getTime();

polyfill/lib/timezone.mjs

@@ -38,7 +38,7 @@ export class TimeZone {
     if (!ES.IsTemporalAbsolute(absolute)) throw new TypeError('invalid Absolute object');
     return ES.GetTimeZoneOffsetString(GetSlot(absolute, EPOCHNANOSECONDS), GetSlot(this, TIMEZONE_ID));
   }
-  getDateTimeFor(absolute) {
+  getDateTimeFor(absolute, calendar = 'iso8601') {
     if (!ES.IsTemporalTimeZone(this)) throw new TypeError('invalid receiver');
     if (!ES.IsTemporalAbsolute(absolute)) throw new TypeError('invalid Absolute object');
     const ns = GetSlot(absolute, EPOCHNANOSECONDS);
@@ -54,7 +54,8 @@ export class TimeZone {
       nanosecond
     } = ES.GetTimeZoneDateTimeParts(ns, GetSlot(this, TIMEZONE_ID));
     const DateTime = GetIntrinsic('%Temporal.DateTime%');
-    return new DateTime(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond);
+    calendar = ES.ToTemporalCalendar(calendar);
+    return new DateTime(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond, calendar);
   }
   getAbsoluteFor(dateTime, options) {
     if (!ES.IsTemporalTimeZone(this)) throw new TypeError('invalid receiver');