Cron Every Saturday

0 3 * * 6

At 03:00 on Saturday

Field by Field

Field	Value	Matches
Minute	0	0
Hour	3	3
Day of month	*	every day
Month	*	every month
Day of week	6	6

Saturday Is 6

The expression fires at 03:00 every Saturday. Named form: 0 3 * * SAT.

Why Saturday Morning Is the Best Maintenance Window

For most business systems Saturday at 3am is the deepest trough in the week: the weekday traffic is gone, the weekly batch has finished, and there are two clear days before Monday morning to notice and fix anything that broke.

That last point is the real argument. A reindex that corrupts something on Saturday morning has 48 hours of slack; the same job on Monday morning has none.

What Belongs Here

• Full backups and backup verification
• Index rebuilds and vacuum operations
• Log rotation and archival
• Certificate renewal checks
• Dependency and security scanning

What Does Not

Anything a customer waits for. A weekend-only job that fails leaves the failure in place until someone checks on Monday — fine for maintenance, unacceptable for delivery.

Time Zones

Standard crontab evaluates in system local time. Vercel Cron, GitHub Actions, Kubernetes CronJobs and AWS EventBridge all evaluate in UTC. If converting your local time crosses midnight, the day-of-week field shifts too — weekdays at 5pm in UTC-07:00 is 0 0 * * 2-6, not 0 0 * * 1-5.

The Day-Field Trap

When both the day-of-month and day-of-week fields are restricted, cron matches either, not both. 0 0 13 * 5 runs on every 13th *and* every Friday — not Friday the 13th. Leave one of them as * unless you genuinely want the union.

Other Common Schedules

Expression	Runs
* * * * *	Every minute
*/5 * * * *	Every 5 minutes
*/15 * * * *	Every 15 minutes
0 * * * *	Every hour, on the hour
0 0 * * *	Every day at midnight
0 9 * * *	Every day at 9am
0 9 * * 1-5	Weekdays at 9am
0 9 * * 1	Every Monday at 9am

Making the Job Safe

• Assume double firing. DST transitions, restarts and retries all cause it. Make the job

idempotent rather than assuming exactly-once.

• Assume overlap. Cron starts the next run whether or not the last one finished. Take a

lock.

• Avoid :00. Every hourly job on the internet fires at the top of the hour; a random

minute spreads load on shared APIs.

• Log the start and end. A cron job that silently stops running is invisible until

someone notices the missing output.

Deploying This Schedule

``bash # crontab -e (system local time) 0 3 * * 6 /usr/local/bin/job.sh >> /var/log/job.log 2>&1 `

`json // vercel.json (UTC) { "crons": [{ "path": "/api/job", "schedule": "0 3 * * 6" }] } `

`yaml # .github/workflows/job.yml (UTC) on: schedule: - cron: '0 3 * * 6' `

Starting from midnight UTC on 1 January 2026, this fires at:

Next runs
2026-01-03 03:00 UTC
2026-01-10 03:00 UTC
2026-01-17 03:00 UTC
2026-01-24 03:00 UTC

At 03:00 on Saturday.

Making It Survive Production

• Redirect output. A cron job with no redirect emails its output to the crontab owner,

and on most servers that mail goes nowhere. Log to a file instead.

• Use absolute paths. Cron runs with a minimal environment — no PATH you recognise,

no shell profile, no nvm. A script that works in your terminal frequently fails here for exactly that reason.

• Escape percent signs. In a crontab, % means newline. date +\%Y needs the

backslash or the command truncates at the percent.

• Take a lock. Cron starts the next run whether or not the last finished. flock` is

one line and prevents the overlap.

• Alert on absence. A job that stops running is silent. Ping a dead-man's-switch service

on success so the *lack* of a ping is what pages you.