[gabipodolnikova]

What: Fixes the 3 failing Timestamp unit tests that have been breaking the Unit tests job on every PR since Oct 29 (no issue filed).

Additional issues: none

What happened

Since Oct 29 the Unit tests job fails with 3 timezone-dependent failures in packages/react-core/src/components/Timestamp/__tests__/Timestamp.test.tsx, e.g.:

expect(screen.getByText('1/1/2022, 5:00:00 AM UTC')).toBeInTheDocument()
Unable to find an element with the text: 1/1/2022, 5:00:00 AM UTC
(rendered: 1/1/2022, 12:00:00 AM Coordinated Universal Time)

The root test script runs jest with TZ=EST. Between the last passing run (Oct 27) and the first failing run (Oct 29), GitHub's ubuntu-latest image migrated from ubuntu-24.04 (20261012.334.1) to ubuntu-26.04 (20261025.179.1) — same Node version. On the newer image, TZ=EST no longer applies the expected UTC−5 offset; jest runs as UTC instead (reproducible locally: TZ=UTC produces exactly these 3 failures, TZ=EST passes).

EST is a legacy POSIX-style abbreviation rather than a real IANA zone, so depending on it is fragile.

The fix

Replace TZ=EST with TZ=America/New_York in the root test script. It is identical to EST (UTC−5, standard time) for every date used in the Timestamp tests — all of them fall in January/February — so no expected values change:

• TZ=America/New_York yarn jest packages/react-core/src/components/Timestamp → 26 passed, 1 skipped
• Full yarn test passes locally with the change

Verification

• yarn test (full suite) on this branch

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