Cron Daily at 2am

0 2 * * *

At 02:00

Field by Field

Field	Value	Matches
Minute	0	0
Hour	2	2
Day of month	*	every day
Month	*	every month
Day of week	*	every day

Why 2am Is Traditional

Two in the morning is after the day's traffic and before the morning batch. It is where maintenance, backups and reindexing have lived for decades.

And Why It Is the Worst Hour for Local Time

Daylight-saving transitions in most of the world happen at 02:00 local. On the spring-forward date the 2am hour does not exist and the job does not run at all; on the fall-back date it exists twice and many cron implementations run the job twice.

0 3 * * * avoids both cases entirely, and costs nothing.

If you must run at 2am, either schedule in UTC (where no transition exists) or make the job idempotent so a duplicate run is harmless.

One Run a Day Needs Monitoring

A daily job that fails has 24 hours to be noticed. Log the completion, alert on a missing completion, and keep the previous run's output until the next one succeeds.

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 2 * * * /usr/local/bin/job.sh >> /var/log/job.log 2>&1 `

`json // vercel.json (UTC) { "crons": [{ "path": "/api/job", "schedule": "0 2 * * *" }] } `

`yaml # .github/workflows/job.yml (UTC) on: schedule: - cron: '0 2 * * *' `

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

Next runs
2026-01-01 02:00 UTC
2026-01-02 02:00 UTC
2026-01-03 02:00 UTC
2026-01-04 02:00 UTC

At 02:00.

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.