Evidence and limitations

How Best Online Clock verifies product facts

Public feature statements are mapped to current source and repeatable tests. This page names the method, review date, and operating limits instead of treating a laboratory score as a universal guarantee.

Fact schema g2_facts_v1 · reviewed September 2, 2026

Review protocol

1. Trace the behavior. Identify the state transition, storage boundary, browser API, and user-visible result in source.
2. Fix the clock. Unit tests use fixed instants for countdown, alarm occurrence, DST, date rollover, and time-zone calculations.
3. Exercise the page. Browser tests cover task completion, keyboard access, responsive layouts, reload/resume behavior, and error states.
4. State the boundary. Claims are rejected or narrowed when audio, notifications, background execution, storage, or device support cannot be guaranteed.

Verified fact registry

Timer deadlines

Running countdowns use an absolute saved deadline and recalculate the remaining time when the page resumes.

Checked-in evidence

src/features/timer/core/countdown.ts
src/features/timer/core/countdown.test.ts
e2e/timer-accuracy.spec.ts

Limit

The tab must remain open. Browser throttling, audio, notifications, and Wake Lock behavior still depend on the browser and device.

Daily browser alarms

Permanent alarms repeat daily at the selected device-local time; snooze choices are 1, 5, or 10 minutes.

Checked-in evidence

src/features/alarm/core/alarm.ts
src/features/alarm/core/alarm-reliability.ts
e2e/g2-alarm-presets.spec.ts

Limit

An alarm is not a background account service. Keep the page open and test sound before relying on it.

Stopwatch timing

The stopwatch uses the browser monotonic performance clock, records laps and splits, and exports the current session as CSV.

Checked-in evidence

src/features/stopwatch/core/stopwatch.ts
src/features/stopwatch/core/stopwatch.test.ts
e2e/stopwatch-accuracy.spec.ts

Limit

Displayed precision is not a calibration certificate and the tool is not intended for safety-critical or regulated timing.

World-time calculation

City clocks use checked-in IANA time-zone identifiers with the browser Intl API; Manila is Asia/Manila, UTC+8, with no current DST rule.

Checked-in evidence

src/data/cities.json
src/features/world-time/core/timezone.ts
src/features/world-time/core/timezone.test.ts

Limit

Time-zone rules come from the browser runtime and can change when governments or runtime data change.

Local tool data

Tool settings, alarms, selected cities, and uploaded background references are stored in the current browser without requiring an account.

Checked-in evidence

src/lib/settings-storage.ts
src/lib/background-image-storage.ts
src/features/alarm/alarm-client.tsx
src/features/world-time/components/multi-city-clock.tsx

Limit

Clearing browser storage or changing devices can remove or separate that local data.

What this page does not claim

Automated Chromium, Firefox, and WebKit checks are useful regression evidence, but they do not replace every physical device, operating-system policy, real Safari build, or future browser version. Real-user performance samples are reported only after their stated observation window and sample gate.

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