fix(jkbrzt#391): timezones

rrule time base is UTC whereas Luxon requires dates in local format to calculate the correct time offset. New tests where introduced to prove correct behaviour in different system timezones. Run those with `npm run test:tz`
spurreiter · Jun 9, 2020 · 90359ed · 90359ed
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diff --git a/README.md b/README.md
@@ -217,7 +217,7 @@ For more examples see
 
 Optionally, it also supports use of the `TZID` parameter in the
 [RFC](https://tools.ietf.org/html/rfc5545#section-3.2.19)
-when the [Luxon](https://github.com/moment/luxon) library is provided. The 
+when the [Luxon](https://github.com/moment/luxon) library is provided. The
 [specification](https://moment.github.io/luxon/docs/manual/zones.html#specifying-a-zone)
 and [support matrix](https://moment.github.io/luxon/docs/manual/matrix.html) for Luxon apply.
 
@@ -230,9 +230,9 @@ new RRule({
   tzid: 'Asia/Tokyo'
 }).all()
 
-// assuming the system timezone is set to America/Los_Angeles, you get:
-[ '2018-01-31T17:30:00.000Z' ]
-// which is the time in Los Angeles when it's 2018-02-01T10:30:00 in Tokyo.
+// regardless of the system timezone, you get:
+[ '2018-02-01T01:30:00.000Z' ]
+// which is the time in UTC when it's 2018-02-01T10:30:00 in Tokyo.
 ```
 
 Whether or not you use the `TZID` param, make sure to only use JS `Date` objects that are
@@ -243,19 +243,22 @@ represented in UTC to avoid unexpected timezone offsets being applied, for examp
 new RRule({
   freq: RRule.MONTHLY,
   dtstart: new Date(2018, 1, 1, 10, 30),
-  until: new Date(2018, 2, 31)
+  until: new Date(2018, 2, 31),
+  tzid: 'Asia/Tokyo'
 }).all()
 
-[ '2018-02-01T18:30:00.000Z', '2018-03-01T18:30:00.000Z' ]
+// assuming your local timezone is Asia/Tokyo
+[ '2018-01-31T16:30:00.000Z', '2018-02-28T16:30:00.000Z' ]
 
 // RIGHT: Will produce dates with recurrences at the correct time
 new RRule({
   freq: RRule.MONTHLY,
   dtstart: new Date(Date.UTC(2018, 1, 1, 10, 30)),
-  until: new Date(Date.UTC(2018, 2, 31))
+  until: new Date(Date.UTC(2018, 2, 31)),
+  tzid: 'Asia/Tokyo'
 }).all()
 
-[ '2018-02-01T10:30:00.000Z', '2018-03-01T10:30:00.000Z' ]
+[ '2018-02-01T01:30:00.000Z', '2018-03-01T01:30:00.000Z' ]
 ```
 
 ### API
@@ -824,4 +827,3 @@ more details.
 #### Related projects
 
 * https://rrules.com/ — RESTful API to get back occurrences of RRULEs that conform to RFC 5545.
-
diff --git a/package.json b/package.json
@@ -28,7 +28,11 @@
     "build": "yarn lint && tsc && webpack && tsc dist/esm/**/*.d.ts",
     "lint": "yarn tslint --project . --fix --config tslint.json",
     "test": "TS_NODE_PROJECT=tsconfig.test.json mocha **/*.test.ts",
-    "test-ci": "TS_NODE_PROJECT=tsconfig.test.json nyc mocha **/*.test.ts"
+    "test-ci": "TS_NODE_PROJECT=tsconfig.test.json nyc mocha **/*.test.ts",
+    "test:tz": "npm run test:tz1 && npm run test:tz2 && npm run test:tz3",
+    "test:tz1": "TZ=Asia/Tokyo npm t",
+    "test:tz2": "TZ=Europe/Madrid npm t",
+    "test:tz3": "TZ=America/Chicago npm t"
   },
   "nyc": {
     "extension": [

diff --git a/src/dateutil.ts b/src/dateutil.ts
@@ -67,7 +67,7 @@ export namespace dateutil {
   /**
    * @return {Number} the date's timezone offset in ms
    */
-  export const tzOffset = function (date: Date) {
+  export const tzOffset = function (date: Date): number {
     return date.getTimezoneOffset() * 60 * 1000
   }
 
@@ -109,7 +109,7 @@ export namespace dateutil {
   /**
    * @return {Number} python-like weekday
    */
-  export const getWeekday = function (date: Date) {
+  export const getWeekday = function (date: Date): number {
     return PY_WEEKDAYS[date.getUTCDay()]
   }
 

diff --git a/src/datewithzone.ts b/src/datewithzone.ts
@@ -33,8 +33,17 @@ export class DateWithZone {
     }
 
     try {
-      const datetime = DateTime
-        .fromJSDate(this.date)
+      const { date } = this
+      const local = new Date(
+        date.getUTCFullYear(),
+        date.getUTCMonth(),
+        date.getUTCDate(),
+        date.getUTCHours(),
+        date.getUTCMinutes(),
+        date.getUTCSeconds(),
+        date.valueOf() % 1000
+      )
+      const datetime = DateTime.fromJSDate(local)
 
       const rezoned = datetime.setZone(this.tzid!, { keepLocalTime: true })
 

diff --git a/test/datewithzone.test.ts b/test/datewithzone.test.ts
@@ -37,8 +37,9 @@ describe('rezonedDate', () => {
     const currentLocalDate = DateTime.local(2000, 2, 6, 1, 0, 0)
     setMockDate(currentLocalDate.toJSDate())
 
-    const d = DateTime.fromISO('20101005T110000').toJSDate()
+    const d = DateTime.fromISO('20101005T110000Z').toJSDate()
     const dt = new DateWithZone(d, targetZone)
+
     expect(dt.rezonedDate()).to.deep.equal(
       expectedDate(DateTime.fromISO('20101005T110000'), currentLocalDate, targetZone)
     )
@@ -63,4 +64,4 @@ describe('rezonedDate', () => {
     DateTime.fromJSDate = origfromJSDate
     resetMockDate()
   })
-})
+})
diff --git a/test/rrule.test.ts b/test/rrule.test.ts
@@ -1,9 +1,8 @@
-import { parse, datetime, testRecurring, expectedDate } from './lib/utils'
+import { parse, datetime, testRecurring } from './lib/utils'
 import { expect } from 'chai'
 import { RRule, rrulestr, Frequency } from '../src/index'
 import { DateTime } from 'luxon'
 import { set as setMockDate, reset as resetMockDate } from 'mockdate'
-import { optionsToString } from '../src/optionstostring';
 
 describe('RRule', function () {
   // Enable additional toString() / fromString() tests
@@ -27,7 +26,7 @@ describe('RRule', function () {
     const s2 = rrulestr(s1).toString()
     expect(s1).equals(s2, s1 + ' => ' + s2)
   })
-  
+
   it('rrulestr itteration not infinite when interval 0', function () {
     ['FREQ=YEARLY;INTERVAL=0;BYSETPOS=1;BYDAY=MO',
     'FREQ=MONTHLY;INTERVAL=0;BYSETPOS=1;BYDAY=MO',
@@ -3664,12 +3663,9 @@ describe('RRule', function () {
         tzid: targetZone
       })
       const recurrence = rule.all()[0]
-      const expected = expectedDate(startDate, currentLocalDate, targetZone)
+      const expected = new Date('2013-08-06T18:00:00.000Z') // regardless in which timezone the local time is, the result in UTC must be the same!
 
-      expect(recurrence)
-        .to.deep.equal(
-          expected 
-        )
+      expect(recurrence).to.deep.equal(expected)
 
       resetMockDate()
     })
@@ -3684,12 +3680,9 @@ describe('RRule', function () {
         tzid: targetZone
       })
       const recurrence = rule.all()[0]
-      const expected = expectedDate(startDate, currentLocalDate, targetZone)
+      const expected = new Date('2013-08-06T18:00:00.000Z') // regardless in which timezone the local time is, the result in UTC must be the same!
 
-      expect(recurrence)
-        .to.deep.equal(
-          expected 
-        )
+      expect(recurrence).to.deep.equal(expected)
 
       resetMockDate()
     })
@@ -3704,11 +3697,11 @@ describe('RRule', function () {
         tzid: targetZone
       })
       const recurrence = rule.after(new Date(0))
-      const expected = expectedDate(startDate, currentLocalDate, targetZone)
+      const expected = new Date('2013-08-06T18:00:00.000Z') // regardless in which timezone the local time is, the result in UTC must be the same!
 
       expect(recurrence)
         .to.deep.equal(
-          expected 
+          expected
         )
 
       resetMockDate()

diff --git a/test/rruleset.test.ts b/test/rruleset.test.ts
@@ -520,17 +520,17 @@ describe('RRuleSet', function () {
       set.rrule(new RRule({
         freq: RRule.YEARLY,
         count: 4,
-        dtstart: DateTime.fromISO('20000101T090000').toJSDate(),
+        dtstart: DateTime.fromISO('20000101T090000Z').toJSDate(), // always use date in UTC
         tzid: targetZone
       }))
 
       set.exdate(
-        DateTime.fromISO('20010101T090000').toJSDate(),
+        DateTime.fromISO('20010101T090000Z').toJSDate(),
       )
 
       set.rdate(
-        DateTime.fromISO('20020301T090000').toJSDate(),
-      )     
+        DateTime.fromISO('20020301T090000Z').toJSDate(),
+      )
 
       expect(set.all()).to.deep.equal([
         expectedDate(DateTime.fromISO('20000101T090000'), currentLocalDate, targetZone),
@@ -564,7 +564,7 @@ describe('RRuleSet', function () {
       set.tzid(targetZone)
 
       set.rdate(
-        DateTime.fromISO('20020301T090000').toJSDate(),
+        DateTime.fromISO('20020301T090000Z').toJSDate(),
       )
 
       expect(set.all()).to.deep.equal([
@@ -755,7 +755,7 @@ describe('RRuleSet', function () {
 
       expect(set.rrules().map(e => e.toString())).eql([rrule.toString()]);
     });
-    
+
     it('exrules()', () => {
       let set = new RRuleSet();
       let rrule = new RRule({
@@ -773,7 +773,7 @@ describe('RRuleSet', function () {
       let set = new RRuleSet();
       let dt = parse('19610201T090000');
       set.rdate(dt);
-      
+
       expect(set.rdates()).eql([dt]);
     });
 
@@ -785,4 +785,4 @@ describe('RRuleSet', function () {
       expect(set.exdates()).eql([dt]);
     });
   });
-});
+});
diff --git a/test/timezones.test.ts b/test/timezones.test.ts
@@ -0,0 +1,43 @@
+import { RRule } from '../src/index'
+import { expect } from "chai"
+
+const ruleByTzid = (tzid: string) => new RRule({
+  freq: RRule.WEEKLY,
+  dtstart: new Date(Date.UTC(2020, 1, 1, 0, 0, 0)), // always use UTC dates!!!
+  tzid,
+  byweekday: [RRule.TU],
+  count: 2
+})
+
+const mapToIso = (arr: Array<Date>): Array<string> =>
+  arr.map(d => d.toISOString())
+
+describe('timezones', () => {
+  it('Europe/Paris', () => {
+    const tzid = 'Europe/Paris'
+    const rule = ruleByTzid(tzid)
+    expect(rule.toString()).to.equal('DTSTART;TZID=Europe/Paris:20200201T000000\nRRULE:FREQ=WEEKLY;BYDAY=TU;COUNT=2')
+    expect(mapToIso(rule.all())).to.deep.equal([
+      '2020-02-03T23:00:00.000Z',
+      '2020-02-10T23:00:00.000Z'
+    ])
+  })
+
+  it('America/New_York', () => {
+    const rule = ruleByTzid('America/New_York')
+    expect(rule.toString()).to.equal('DTSTART;TZID=America/New_York:20200201T000000\nRRULE:FREQ=WEEKLY;BYDAY=TU;COUNT=2')
+    expect(mapToIso(rule.all())).to.deep.equal([
+      '2020-02-04T05:00:00.000Z',
+      '2020-02-11T05:00:00.000Z'
+    ])
+  })
+
+  it('UTC', () => {
+    const rule = ruleByTzid('UTC')
+    expect(rule.toString()).to.equal('DTSTART:20200201T000000Z\nRRULE:FREQ=WEEKLY;BYDAY=TU;COUNT=2')
+    expect(mapToIso(rule.all())).to.deep.equal([
+      '2020-02-04T00:00:00.000Z',
+      '2020-02-11T00:00:00.000Z'
+    ])
+  })
+})