~/cron-builder

Cron: daily at 3 AM

The cron expression `0 3 * * *` fires once a day at 03:00. Classic nightly-batch window. What goes wrong with DST and how to avoid it.

# expression

0 3 * * *

Means: At minute 0 of hour 3, every day — once a day at 03:00 sharp.

→ Open in cron builder (pre-filled)

# common use cases

• Nightly database backups during the off-peak window.
• Log rotation, anti-spam recomputation, end-of-day reports.
• Cache warmups before the morning traffic peak.

# next fires (sample)

• Day 1 03:00
• Day 2 03:00
• Day 3 03:00
• Day 4 03:00
• Day 5 03:00

# pitfalls

• On the spring-forward DST day, 02:00 → 03:00 instantly. The 03:00 fire may be skipped or fire at 04:00 depending on runner. Schedule in UTC to avoid.
• If multiple nightly jobs run at 03:00 they pile up. Stagger: one at 03:00, next at 03:15, etc.

# other patterns

• Cron: every 5 minutes — */5 * * * *
• Cron: every 15 minutes — */15 * * * *
• Cron: every hour — 0 * * * *
• Cron: weekdays at 9 AM — 0 9 * * 1-5
• Cron: first of every month at midnight — 0 0 1 * *
• Cron: annually (Jan 1 at midnight) — 0 0 1 1 *

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