Cron timezone issues: why your job runs at the wrong time and how to fix it

How this is calculated

On a UTC server, a 0 2 * * * job runs at 2 AM UTC. If you're in US Eastern time and thought '2 AM my time,' the job actually fires at 10 PM Eastern (or 9 PM depending on DST). The fix is to either set CRON_TZ=America/New_York in your crontab or adjust the hours: 0 7 * * * for 2 AM Eastern in standard time, 0 6 * * * during DST. For DST spring-forward, cron skips the hour that doesn't exist. For fall-back, cron runs the job twice for the repeated hour (typically at the first occurrence). If your job is idempotent this is fine. If not, add a guard.

Verdict

Always set CRON_TZ in your crontab if you care about local time. Prefer UTC for server jobs and document that decision. For DST safety, either accept the skip/double behavior (which is usually harmless for idempotent jobs) or switch to systemd timers with a monotonic calendar event.