Time zone scheduling
Test the clock time that does not happen in Sydney
Daylight-saving boundaries reveal hidden scheduling defaults. Use a known transition and assert the product's chosen gap and overlap behaviour.
In this article
Select a concrete transition
The NSW Government states that on 4 October 2026 clocks move from 2 am to 3 am. A Sydney schedule for 2:30 am therefore needs the application's nonexistent-time policy on that date.
Create a synthetic schedule and calculate its surrounding occurrences using the actual runtime and time-zone data. Do not hard-code a UTC offset into the test setup.
Record whether the intended outcome is skip, shift or another explicitly supported behaviour.
Assert the resolved occurrence
Inspect the calculated instant and the user-visible preview. They should describe the same policy.
If the scheduler skips the occurrence while the UI promises a later run, the product is inconsistent even if each component follows its own documented default.
Use a controlled clock or schedule-resolution test so the exercise does not depend on waiting for the calendar date.
Test the repeated interval separately
The NSW Government lists the next return from daylight saving as 4 April 2027, when clocks move from 3 am back to 2 am. Test a local time in that repeated interval under the chosen once-or-twice policy.
Verify occurrence identities so repeated local clock text does not accidentally collapse two intended runs or create a duplicate where only one is allowed.
Also test a normal date on either side to ensure the special handling does not shift ordinary schedules.
Include restart and catch-up
Restart the scheduler between calculation and execution, then retry the worker after a simulated lost response. Confirm that the same occurrence does not produce the effect twice.
Simulate the service being unavailable through the transition and apply the missed-execution policy. Catching up is a separate decision from resolving a nonexistent local time.
Keep the transition dates and expected outcomes in the test record, with a source review when time-zone rules change. The goal is a verified business policy, not merely confidence that the date library has some daylight-saving support.
Primary sources
NSW Government: daylight savingReferences checked 11 September 2026.