Treat the System time since Epoch as a bigint (#58)

Author: 12wrigja

lib/ecmascript.ts

@@ -55,10 +55,10 @@ import {
   NANOSECONDS
 } from './slots';
 import { IsBuiltinCalendar } from './calendar';
-
-const DAYMILLIS = 86400000;
-const NS_MIN = bigInt(-86400).multiply(1e17);
-const NS_MAX = bigInt(86400).multiply(1e17);
+const DAY_SECONDS = 86400;
+const DAY_NANOS = bigInt(DAY_SECONDS).multiply(1e9);
+const NS_MIN = bigInt(-DAY_SECONDS).multiply(1e17);
+const NS_MAX = bigInt(DAY_SECONDS).multiply(1e17);
 const YEAR_MIN = -271821;
 const YEAR_MAX = 275760;
 const BEFORE_FIRST_DST = bigInt(-388152).multiply(1e13); // 1847-01-01T00:00:00Z
@@ -2266,13 +2266,13 @@ export const ES = ObjectAssign({}, ES2020, {
     return ES.BalanceISODateTime(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond);
   },
   GetIANATimeZoneNextTransition: (epochNanoseconds, id) => {
-    const uppercap = ES.SystemUTCEpochNanoSeconds() + 366 * DAYMILLIS * 1e6;
+    const uppercap = ES.SystemUTCEpochNanoSeconds().plus(DAY_NANOS.multiply(366));
     let leftNanos = epochNanoseconds;
     const leftOffsetNs = ES.GetIANATimeZoneOffsetNanoseconds(leftNanos, id);
     let rightNanos = leftNanos;
     let rightOffsetNs = leftOffsetNs;
     while (leftOffsetNs === rightOffsetNs && bigInt(leftNanos).compare(uppercap) === -1) {
-      rightNanos = bigInt(leftNanos).plus(2 * 7 * DAYMILLIS * 1e6);
+      rightNanos = bigInt(leftNanos).plus(DAY_NANOS.multiply(2 * 7));
       rightOffsetNs = ES.GetIANATimeZoneOffsetNanoseconds(rightNanos, id);
       if (leftOffsetNs === rightOffsetNs) {
         leftNanos = rightNanos;
@@ -2295,7 +2295,7 @@ export const ES = ObjectAssign({}, ES2020, {
     let leftNanos = rightNanos;
     let leftOffsetNs = rightOffsetNs;
     while (rightOffsetNs === leftOffsetNs && bigInt(rightNanos).compare(lowercap) === 1) {
-      leftNanos = bigInt(rightNanos).minus(2 * 7 * DAYMILLIS * 1e6);
+      leftNanos = bigInt(rightNanos).minus(DAY_NANOS.multiply(2 * 7));
       leftOffsetNs = ES.GetIANATimeZoneOffsetNanoseconds(leftNanos, id);
       if (rightOffsetNs === leftOffsetNs) {
         rightNanos = leftNanos;
@@ -2331,10 +2331,9 @@ export const ES = ObjectAssign({}, ES2020, {
   GetIANATimeZoneEpochValue: (id, year, month, day, hour, minute, second, millisecond, microsecond, nanosecond) => {
     const ns = ES.GetEpochFromISOParts(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond);
     if (ns === null) throw new RangeError('DateTime outside of supported range');
-    const dayNanos = bigInt(DAYMILLIS).multiply(1e6);
-    let nsEarlier = ns.minus(dayNanos);
+    let nsEarlier = ns.minus(DAY_NANOS);
     if (nsEarlier.lesser(NS_MIN)) nsEarlier = ns;
-    let nsLater = ns.plus(dayNanos);
+    let nsLater = ns.plus(DAY_NANOS);
     if (nsLater.greater(NS_MAX)) nsLater = ns;
     const earliest = ES.GetIANATimeZoneOffsetNanoseconds(nsEarlier, id);
     const latest = ES.GetIANATimeZoneOffsetNanoseconds(nsLater, id);

test/timezone.mjs

@@ -417,6 +417,8 @@ describe('TimeZone', () => {
   });
   describe('getNextTransition works', () => {
     const nyc = Temporal.TimeZone.from('America/New_York');
+    const noTransitionTZ = Temporal.TimeZone.from('Etc/GMT+10');
+
     it('should not have bug #510', () => {
       // See https://github.com/tc39/proposal-temporal/issues/510 for more.
       const a1 = Temporal.Instant.from('2019-04-16T21:01Z');
@@ -430,6 +432,10 @@ describe('TimeZone', () => {
       equal(`${nyc.getNextTransition(inst)}`, '2019-03-10T07:00:00Z');
       equal(`${nyc.getNextTransition(nyc.getNextTransition(inst))}`, '2019-11-03T06:00:00Z');
     });
+    it('should work for timezones with no scheduled transitions in the near future', () => {
+      const start = Temporal.Instant.from('1945-10-15T13:00:00Z');
+      equal(noTransitionTZ.getNextTransition(start), null);
+    });
     it('casts argument', () => {
       equal(`${nyc.getNextTransition('2019-04-16T21:01Z')}`, '2019-11-03T06:00:00Z');
     });