Clamp dates to supported range.

We no longer throw an error when an out-of-range date is constructed.
Instead, if an epoch timestamp is used that is too small or large, we
clamp the range to our supported min/max.

packages/cldr-core/__tests__/api/calendars/fromfields.test.ts

@@ -19,8 +19,11 @@ test('gregorian bounds', () => {
   let d: CalendarDate;
   const api = calendarsApi('en');
 
-  expect(() => api.newGregorianDate({ year: -9999 })).toThrow();
-  expect(() => api.newGregorianDate({ year: 9999 })).toThrow();
+  d = api.newGregorianDate({ year: -9999 });
+  expect(d.toString()).toEqual('Gregorian -4712-01-01 00:00:00.000 Etc/UTC');
+
+  d = api.newGregorianDate({ year: 9999 });
+  expect(d.toString()).toEqual('Gregorian 8652-12-31 00:00:00.000 Etc/UTC');
 
   d = api.newGregorianDate({ year: 2020, month: -1 });
   expect(d.toString()).toEqual('Gregorian 2020-01-01 00:00:00.000 Etc/UTC');
@@ -194,9 +197,13 @@ test('persian defaults', () => {
 
 test('persian bounds', () => {
   const api = calendarsApi('en');
+  let d: CalendarDate;
+
+  d = api.newPersianDate({ year: -9999 });
+  expect(d.toString()).toEqual('Persian -5334-09-03 00:00:00.000 Etc/UTC');
 
-  expect(() => api.newPersianDate({ year: -9999 })).toThrow();
-  expect(() => api.newPersianDate({ year: 9999 })).toThrow();
+  d = api.newPersianDate({ year: 9999 });
+  expect(d.toString()).toEqual('Persian 8031-10-11 00:00:00.000 Etc/UTC');
 });
 
 test('persian from fields', () => {

packages/cldr-core/__tests__/systems/calendars/gregorian.test.ts

@@ -4,6 +4,11 @@ import { CalendarDate, GregorianDate } from '../../../src';
 
 const make = (e: number, z: string) => GregorianDate.fromUnixEpoch(e, z, DayOfWeek.SUNDAY, 1);
 
+const unixEpochFromJD = (jd: number, msDay: number = 0): number => {
+  const days = jd - CalendarConstants.JD_UNIX_EPOCH;
+  return days * CalendarConstants.ONE_DAY_MS + Math.round(msDay);
+};
+
 const NEW_YORK = 'America/New_York';
 const LOS_ANGELES = 'America/Los_Angeles';
 const PARIS = 'Europe/Paris';
@@ -107,33 +112,25 @@ test('gregorian date', () => {
   expect(d.yearOfWeekOfYear()).toEqual(2018);
 });
 
-test('min / max date', () => {
-  let d: GregorianDate;
-  let n: number;
+test('min / max / clamp', () => {
+  let d: CalendarDate;
 
-  const unix = CalendarConstants.JD_UNIX_EPOCH;
+  const min = unixEpochFromJD(CalendarConstants.JD_MIN, 0);
+  const max = unixEpochFromJD(CalendarConstants.JD_MAX, 0);
 
-  n = (unix - 1) * CalendarConstants.ONE_DAY_MS;
-  d = make(-n, NEW_YORK);
-  expect(d.era()).toEqual(0);
-  expect(d.extendedYear()).toEqual(-4712);
-  expect(d.year()).toEqual(4713);
-  expect(d.month()).toEqual(1); // Jan
-  expect(d.dayOfMonth()).toEqual(1);
+  d = make(min, 'UTC');
+  expect(d.toString()).toEqual('Gregorian -4712-01-01 00:00:00.000 Etc/UTC');
 
-  // Attempting to represent Dec 31 4714 BC
-  expect(() => make(-n - CalendarConstants.ONE_DAY_MS, NEW_YORK)).toThrowError();
+  // Clamp to minimum date
+  d = make(min - CalendarConstants.ONE_DAY_MS, 'UTC');
+  expect(d.toString()).toEqual('Gregorian -4712-01-01 00:00:00.000 Etc/UTC');
 
-  n = (CalendarConstants.JD_MAX - unix + 1) * CalendarConstants.ONE_DAY_MS;
-  d = make(n, NEW_YORK);
-  expect(d.era()).toEqual(1);
-  expect(d.extendedYear()).toEqual(8652);
-  expect(d.year()).toEqual(8652);
-  expect(d.month()).toEqual(12); // Dec
-  expect(d.dayOfMonth()).toEqual(31);
+  d = make(max, 'UTC');
+  expect(d.toString()).toEqual('Gregorian 8652-12-31 00:00:00.000 Etc/UTC');
 
-  // Attempt to represent Jan  1 8653 AD
-  expect(() => make(n + CalendarConstants.ONE_DAY_MS, NEW_YORK)).toThrowError();
+  // Clamp to maximum date
+  d = make(max + CalendarConstants.ONE_DAY_MS, 'UTC');
+  expect(d.toString()).toEqual('Gregorian 8652-12-31 00:00:00.000 Etc/UTC');
 });
 
 test('millis in day', () => {

packages/cldr-core/src/systems/calendars/calendar.ts

@@ -1,7 +1,7 @@
 import { DateTimePatternField, DateTimePatternFieldType, MetaZoneType } from '@phensley/cldr-types';
 
 import { dateFields, DateField, DayOfWeek } from './fields';
-import { CalendarConstants, ConstantsDesc } from './constants';
+import { CalendarConstants } from './constants';
 import { substituteZoneAlias, zoneInfoFromUTC, ZoneInfo } from './timezone';
 import { INTERNAL_NUMBERING } from '../numbering';
 import { timePeriodFieldFlags, TimePeriod, TimePeriodField, TimePeriodFieldFlag, TIME_PERIOD_FIELDS } from './interval';
@@ -972,8 +972,8 @@ const jdFromUnixEpoch = (ms: number, f: number[]): void => {
  * is relative to these.
  */
 const computeBaseFields = (f: number[]): void => {
-  const jd = f[DateField.JULIAN_DAY];
-  checkJDRange(jd);
+  const jd = clamp(f[DateField.JULIAN_DAY], CalendarConstants.JD_MIN, CalendarConstants.JD_MAX);
+  // checkJDRange(jd);
 
   let msDay = f[DateField.MILLIS_IN_DAY];
   const ms = msDay + (jd - CalendarConstants.JD_UNIX_EPOCH) * CalendarConstants.ONE_DAY_MS;
@@ -1001,14 +1001,15 @@ const computeBaseFields = (f: number[]): void => {
   f[DateField.DAY_OF_WEEK] = dow;
 };
 
-const checkJDRange = (jd: number): void => {
-  if (jd < CalendarConstants.JD_MIN || jd > CalendarConstants.JD_MAX) {
-    throw new Error(
-      `Julian day ${jd} is outside the supported range of this library: ` +
-        `${ConstantsDesc.JD_MIN} to ${ConstantsDesc.JD_MAX}`,
-    );
-  }
-};
+// TODO: clamp range instead of throwing error.
+// const checkJDRange = (jd: number): void => {
+//   if (jd < CalendarConstants.JD_MIN || jd > CalendarConstants.JD_MAX) {
+//     throw new Error(
+//       `Julian day ${jd} is outside the supported range of this library: ` +
+//         `${ConstantsDesc.JD_MIN} to ${ConstantsDesc.JD_MAX}`,
+//     );
+//   }
+// };
 
 /**
  * Given a Julian day and local milliseconds (in UTC), return the Unix

packages/cldr-core/src/systems/calendars/constants.ts

@@ -4,8 +4,8 @@ export const enum CalendarConstants {
   // TODO: revisit to expand range of julian days
 
   // Min and max Julian day form a range of full years whose midpoint is the
-  // UNIX epoch Jan 1 1970
-  MIN_YEAR = 4713,
+  // UNIX epoch Jan 1 1970. The goal is to constrain the epoch
+  // timestamps to a reasonable range. This range may expand in the future.
 
   // Mon Jan  1 4713 BC
   JD_MIN = 0,

packages/cldr-core/src/systems/calendars/gregorian.ts

@@ -247,6 +247,7 @@ const computeJulianFields = (f: number[]): void => {
   if (doy >= mar1) {
     corr = isLeap ? 1 : 2;
   }
+
   const month = floor((12 * (doy + corr) + 6) / 367);
   const dom = doy - MONTH_COUNT[month][isLeap ? 3 : 2] + 1;