● Vendor-neutral preflight

Make the clock change
prove itself.

Turn declared local working hours into an inspectable DST test matrix. Catch missing, repeated, or shifted boundary cases before an invitee does.

Build expected fixture How the audit works

Runtime: Local only
Rules: Browser IANA
Export: CSV + ICS

Pixel-art observatory with two clock towers and an amber daylight-saving boundary crossing a world-time grid — FIG 01 Civil time has seams. Test where the rules split.

01–02

Audit configuration

Define the promise, then stress the boundary.

Hours are interpreted in the organizer zone exactly as written. Choose a comparison zone to see what an invitee should receive.

01 Declare weekly local hours

Closed days produce no expected slots. One continuous window per day is supported in v1.

02 Choose zones and dates

Organizer timezone Comparison timezone

Use IANA names such as Europe/London or America/New_York, not abbreviations like EST.

Start date End date

Configuration is saved only in this browser after a run.

Computed fixture

Boundary report

Interpretation guide

Expected slots, not vendor parity.

Anchor the promise

Each date starts from the declared organizer wall time. UTC is derived from the browser’s current IANA timezone rules.

Expose the seam

The matrix labels the first scheduled window after an offset change, plus local times that repeat or never occur.

Compare evidence

Use the CSV or ICS fixture beside a booking page. A mismatch is evidence to investigate, not a claim about a vendor’s internal logic.

How does the audit handle ambiguous local time?

When clocks move back, one wall time can map to two real instants. Both are detected and the row is marked “Review”; the ICS fixture chooses the earlier occurrence and says so in its description. When clocks jump forward, a missing wall time is marked invalid and omitted from ICS.