From b482707c47d524856608a0a13fd3522cd4b68680 Mon Sep 17 00:00:00 2001
From: Philip Chimento <pchimento@igalia.com>
Date: Wed, 10 Jun 2020 15:31:36 -0700
Subject: [PATCH] Add Gregorian calendar

This is identical to the ISO8601 calendar, except for ISO week numbering
rules, which we do not currently use in Temporal.

See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Locale/calendar
---
 polyfill/lib/calendar.mjs   | 9 +++++++++
 polyfill/lib/ecmascript.mjs | 3 ++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/polyfill/lib/calendar.mjs b/polyfill/lib/calendar.mjs
index 3682b6f2f0..480eb054b1 100644
--- a/polyfill/lib/calendar.mjs
+++ b/polyfill/lib/calendar.mjs
@@ -203,3 +203,12 @@ export class ISO8601 extends Calendar {
     return ES.LeapYear(GetSlot(date, ISO_YEAR));
   }
 }
+
+// According to documentation for Intl.Locale.prototype.calendar on MDN,
+// 'iso8601' calendar is equivalent to 'gregory' except for ISO 8601 week
+// numbering rules, which we do not currently use in Temporal.
+export class Gregorian extends ISO8601 {
+  constructor() {
+    super('gregory');
+  }
+}
diff --git a/polyfill/lib/ecmascript.mjs b/polyfill/lib/ecmascript.mjs
index d6aee90d84..6a785d20d8 100644
--- a/polyfill/lib/ecmascript.mjs
+++ b/polyfill/lib/ecmascript.mjs
@@ -6,7 +6,7 @@ const ObjectAssign = Object.assign;
 import bigInt from 'big-integer';
 
 import { GetIntrinsic } from './intrinsicclass.mjs';
-import { ISO8601 as CalendarISO8601 } from './calendar.mjs';
+import { Gregorian as CalendarGregorian, ISO8601 as CalendarISO8601 } from './calendar.mjs';
 import {
   GetSlot,
   HasSlot,
@@ -43,6 +43,7 @@ const YEAR_MIN = -271821;
 const YEAR_MAX = 275760;
 
 const BUILTIN_CALENDARS = {
+  gregory: CalendarGregorian,
   iso8601: CalendarISO8601
   // To be filled in as builtin calendars are implemented
 };