Europe changed clocks on Sunday, the US does it next Sunday. Check your scheduled posts

Description and use

During the DST transition week in Europe and the US, scheduled tasks using fixed offsets misfire by an hour. The fix is to store IANA zones, compute UTC at run time, pin cron to the zone, and handle ambiguous hours idempotently.

Problem

Scheduled jobs, social posts, newsletters, and cron tasks misfire by an hour during the week when Europe and the US change daylight‑saving time offsets.

Outcome

By storing IANA zone names, computing UTC instants at run time, pinning cron zones, handling ambiguous hours idempotently, and updating the UI, scheduled tasks no longer misfire during DST transitions.

Workflow

• Identify scheduled items stored with raw offsets and convert them to IANA zone names.
• Compute the next run UTC instant using the zone and local time (e.g., with Luxon’s setZone and plus).
• Pin cron jobs to the correct zone (CRON_TZ or node‑cron timezone option) or schedule hourly and check local time inside the job.
• Make jobs idempotent for ambiguous hours by using a run key such as jobId+localDate.
• Update UI to show the audience’s time zone next to the scheduled time.
• Audit the database or sheet for raw offsets, list items between now and Nov 2 that cross the US/EU gap, and test cross‑zone scheduling this week.

Evidence

Storing "9:00 +02:00" instead of "9:00 Europe/Madrid"

Source

Store the IANA zone name next to the local time and compute the UTC instant for each run, not once at creation time.

Source

Server cron in UTC, humans thinking in local time

Source

Make jobs idempotent with a run key like jobId + localDate so the second one is a no‑op.

Source

Show the audience’s zone next to the time, always.

Source