Parse zone-less playlist date-times as UTC

src/loader/date-range.ts

@@ -1,4 +1,5 @@
 import { AttrList } from '../utils/attr-list';
+import { parseDateTime } from '../utils/date-time';
 import { logger } from '../utils/logger';
 import type { MediaFragmentRef } from './fragment';
 
@@ -90,12 +91,14 @@ export class DateRange {
       this._endDate = dateRangeWithSameId._endDate;
       this._dateAtEnd = dateRangeWithSameId._dateAtEnd;
     } else {
-      this._startDate = new Date(dateRangeAttr[DateRangeAttribute.START_DATE]);
+      this._startDate = new Date(
+        parseDateTime(dateRangeAttr[DateRangeAttribute.START_DATE]),
+      );
     }
     if (DateRangeAttribute.END_DATE in dateRangeAttr) {
       const endDate =
         dateRangeWithSameId?.endDate ||
-        new Date(dateRangeAttr[DateRangeAttribute.END_DATE]);
+        new Date(parseDateTime(dateRangeAttr[DateRangeAttribute.END_DATE]));
       if (Number.isFinite(endDate.getTime())) {
         this._endDate = endDate;
       }

src/loader/fragment.ts

@@ -1,6 +1,7 @@
 import { buildAbsoluteURL } from 'url-toolkit';
 import { LoadStats } from './load-stats';
 import { PlaylistLevelType } from '../types/loader';
+import { parseDateTime } from '../utils/date-time';
 import type { LevelKey } from './level-key';
 import type {
   FragmentLoaderContext,
@@ -337,7 +338,7 @@ export class Fragment extends BaseSegment {
 
   get programDateTime(): number | null {
     if (this._programDateTime === null && this.rawProgramDateTime) {
-      this.programDateTime = Date.parse(this.rawProgramDateTime);
+      this.programDateTime = parseDateTime(this.rawProgramDateTime);
     }
     return this._programDateTime;
   }

src/utils/date-time.ts

@@ -0,0 +1,24 @@
+import { logger } from './logger';
+
+// 'Z' or a UTC offset (+05:00, -0500, +05) at the end of a date-time string
+const ZONE_DESIGNATOR = /(?:[Zz]|[+-]\d{2}(?::?\d{2})?)$/;
+
+let warnedZoneless = false;
+
+// ISO 8601 date-times without a time zone represent local time, and
+// `Date.parse` follows that. HLS supersedes it: clients SHOULD treat a
+// date-time without a time zone as UTC (rfc8216bis-17 Section 4.4.4.6),
+// matching Apple's clients. Playlists SHOULD indicate a time zone, so the
+// first zone-less value parsed logs a warning.
+export function parseDateTime(value: string): number {
+  if (/[Tt]/.test(value) && !ZONE_DESIGNATOR.test(value)) {
+    if (!warnedZoneless) {
+      warnedZoneless = true;
+      logger.warn(
+        `Date/time "${value}" has no time zone. Parsing as UTC (playlists SHOULD indicate a time zone).`,
+      );
+    }
+    return Date.parse(value + 'Z');
+  }
+  return Date.parse(value);
+}

tests/index.js

@@ -49,6 +49,7 @@ import './unit/utils/binary-search';
 import './unit/utils/buffer-helper';
 import './unit/utils/cea-608-parser';
 import './unit/utils/codecs';
+import './unit/utils/date-time';
 import './unit/utils/error-helper';
 import './unit/utils/fetch-loader';
 import './unit/utils/discontinuities';

tests/unit/loader/date-range.ts

@@ -110,6 +110,20 @@ describe('DateRange class', function () {
     expect(dateRangeEndDate.duration).to.equal(60.001);
   });
 
+  it('parses zone-less START-DATE and END-DATE as UTC', function () {
+    const zonelessDates = new AttrList(
+      'ID="ad5",START-DATE="2020-01-02T21:55:44.000",END-DATE="2020-01-02T21:56:44.001"',
+    );
+    const dateRange = new DateRange(zonelessDates);
+    expect(dateRange.isValid).to.be.true;
+    expect(dateRange.startDate.toISOString()).to.equal(
+      '2020-01-02T21:55:44.000Z',
+    );
+    expect((dateRange.endDate as Date).toISOString()).to.equal(
+      '2020-01-02T21:56:44.001Z',
+    );
+  });
+
   it('merges tags with matching ID attributes', function () {
     const scteOut = new DateRange(sctePlanned);
     const scteIn = new DateRange(scteDurationUpdate, scteOut);

tests/unit/loader/m3u8-parser.ts

@@ -1349,6 +1349,28 @@ Rollover38803/20160525T064049-01-69844069.ts
     expect(result.fragments[2].programDateTime).to.equal(1464366904000);
   });
 
+  it('parses #EXT-X-PROGRAM-DATE-TIME without a time zone as UTC', function () {
+    const level = `#EXTM3U
+#EXT-X-VERSION:2
+#EXT-X-TARGETDURATION:10
+#EXT-X-MEDIA-SEQUENCE:69844067
+#EXTINF:10, no desc
+#EXT-X-PROGRAM-DATE-TIME:2016-05-27T16:34:44.000
+Rollover38803/20160525T064049-01-69844067.ts
+    `;
+    const result = M3U8Parser.parseLevelPlaylist(
+      level,
+      'http://video.example.com/disc.m3u8',
+      0,
+      PlaylistLevelType.MAIN,
+      0,
+      null,
+    );
+    expect(result.playlistParsingError).to.be.null;
+    expect(result.hasProgramDateTime).to.be.true;
+    expect(result.fragments[0].programDateTime).to.equal(1464366884000);
+  });
+
   it('parses delta playlists with one #EXT-X-PROGRAM-DATE-TIME after segments', function () {
     const level = `#EXTM3U
 #EXT-X-TARGETDURATION:6

tests/unit/utils/date-time.ts

@@ -0,0 +1,24 @@
+import { expect } from 'chai';
+import { parseDateTime } from '../../../src/utils/date-time';
+
+describe('parseDateTime', function () {
+  it('parses date-times with a time zone as-is', function () {
+    expect(parseDateTime('2016-05-27T16:34:44Z')).to.equal(1464366884000);
+    expect(parseDateTime('2016-05-27T16:34:44.000Z')).to.equal(1464366884000);
+    expect(parseDateTime('2016-05-27T19:34:44+03:00')).to.equal(1464366884000);
+    expect(parseDateTime('2016-05-27T13:34:44-03:00')).to.equal(1464366884000);
+  });
+
+  it('parses zone-less date-times as UTC', function () {
+    expect(parseDateTime('2016-05-27T16:34:44')).to.equal(1464366884000);
+    expect(parseDateTime('2016-05-27T16:34:44.000')).to.equal(1464366884000);
+  });
+
+  it('leaves date-only values alone (already UTC per ECMA-262)', function () {
+    expect(parseDateTime('2016-05-27')).to.equal(1464307200000);
+  });
+
+  it('returns NaN for invalid input', function () {
+    expect(parseDateTime('not a date')).to.be.NaN;
+  });
+});