davesecops opened a new issue, #21538:
URL: https://github.com/apache/echarts/issues/21538
### Version
6.0.0 (bug present on current `master`)
### Link to Minimal Reproduction
N/A — this is a test-only bug. Run `npm run test` in any DST-observing
timezone (US, EU, Australia, NZ, Brazil, etc.).
### Steps to Reproduce
1. Clone apache/echarts, `npm install`
2. Set system timezone to any DST-observing zone (e.g., America/New_York,
Europe/Berlin, Australia/Sydney)
3. Run `npm run test`
4. Observe `roundTime_locale` test failure in
`test/ut/spec/util/time.test.ts`
### Current Behavior
```
FAIL test/ut/spec/util/time.test.ts
● util/time › roundTime › roundTime_locale
expect(received).toEqual(expected) // deep equality
Expected: 528526800000
Received: 528523200000
at Object.<anonymous> (spec/util/time.test.ts:166:18)
```
The 3,600,000ms difference (exactly 1 hour) is the DST offset.
### Expected Behavior
All unit tests should pass regardless of the machine's timezone.
### Root Cause
The `getISOTimezone()` helper in `time.test.ts` computes the UTC offset from
`new Date(0)` (January 1, 1970) and applies that fixed offset string to
construct expected dates across different months:
```typescript
function getISOTimezone(): string {
const offsetMinutes = (new Date(0)).getTimezoneOffset(); // ← always
January offset
// ...
}
// Then used for October dates:
new Date(\`1986-10-01T00:00:00.000\${timezoneStr}\`) // ← January offset
applied to October
```
In DST-observing timezones, the offset in January differs from October. For
example, US Eastern:
- January: UTC-5 (EST)
- October: UTC-4 (EDT)
So `getISOTimezone()` returns `-05:00`, but `new
Date('1986-10-01T00:00:00.000-05:00')` constructs midnight EST, which is 1AM
EDT. Meanwhile `roundTime()` correctly rounds to midnight local time (EDT),
producing a 1-hour mismatch.
The `roundTime_UTC` test passes because it uses `.toISOString()` which is
timezone-independent.
### Environment
- **OS:** Any (macOS, Linux, Windows)
- **Node:** 18+
- **Timezone:** Any DST-observing timezone (fails in ~70% of world timezones)
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