Mastering Cron Jobs: Run a Script Every 5 Minutes Only on a Specific Date and Time

Cron is one of the most powerful scheduling tools available on Linux and Unix systems. Most developers know how to schedule a task every minute, every hour, or every day. However, many people struggle when they need to execute a script only on a specific date and during a specific time window.

This article explains how to achieve that cleanly and reliably.

Understanding Cron

A cron expression consists of five fields:

* * * * * command
│ │ │ │ │
│ │ │ │ └── Day of Week (0-7)
│ │ │ └──── Month
│ │ └────── Day of Month
│ └──────── Hour
└────────── Minute

For example:

*/5 * * * * /path/to/script.sh

This executes the script every 5 minutes, every hour, every day.

But what if you want something more specific?

Scenario 1

Run Every 5 Minutes Only on a Specific Date and Hour

Suppose you want to execute a script:

• Date: 20 July 2026
• Time: 2:00 PM – 2:59 PM
• Frequency: Every 5 minutes

A simple cron entry can do this:

*/5 14 20 7 * [ "$(date +\%Y-\%m-\%d)" = "2026-07-20" ] && /path/to/script.sh

How It Works

• */5 → Every 5 minutes
• 14 → Hour 14 (2 PM)
• 20 → 20th day
• 7 → July

date +%Y-%m-%d ensures the year is 2026

Without the year check, the cron would execute every year on July 20.

Scenario 2

Run Every 5 Minutes Between Two Times

Imagine you want:

• Date: 20 July 2026
• Start: 2:15 PM
• End: 3:45 PM

Every 5 minutes

Use:

*/5 * * * * if [ "$(date +\%Y-\%m-\%d)" = "2026-07-20" ]; then
    now=$(date +\%H\%M)
    [ "$now" -ge 1415 ] && [ "$now" -le 1545 ] && /path/to/script.sh
fi

What Happens?

Cron wakes up every 5 minutes.

The script only executes if:

• Today's date is 2026-07-20
• Current time is between 14:15 and 15:45

Scenario 3

Execute Once at an Exact Time

Need to run a script only once?

Example:

• 20 July
• 2:30 PM

30 14 20 7 * /path/to/script.sh

This runs every year on July 20 at 2:30 PM.

Run Only Once in a Specific Year

Cron does not support a year field.

Many developers don't realize this.

If you need a task to execute only once in 2026, use the at command:

echo "/path/to/script.sh" | at 2:30 PM Jul 20 2026

The job is executed once and automatically removed from the queue.

Why Cron Doesn't Support Years

Cron was intentionally designed for recurring schedules.

Its philosophy is:

• every minute
• every hour
• every day
• every week
• every month

A specific year isn't part of the original cron specification.

If you require year-aware scheduling, you generally have three options:

1. Check the year inside your command.
2. Use the at scheduler.
3. Use a more advanced scheduler such as systemd timers, Jenkins, Kubernetes CronJobs, Airflow, or cloud schedulers.

Best Practices

Always Use Absolute Paths

Bad:

python script.py

Good:

/usr/bin/python3 /home/user/scripts/script.py

Redirect Logs

*/5 * * * * /path/to/script.sh >> /var/log/script.log 2>&1

This makes debugging much easier.

Use Full Environment Variables

Cron runs with a minimal environment.

Instead of:

python

Use:

/usr/bin/python3

Similarly:

/usr/bin/bash
/usr/bin/php
/usr/bin/node

Test Before Scheduling

Run your script manually first:

bash /path/to/script.sh

If it fails manually, cron won't magically fix it.

Common Mistakes

❌ Forgetting to escape %

Inside cron:

date +%Y

Should become:

date +\%Y

Otherwise % is interpreted as a newline by cron.

❌ Using relative paths

./backup.sh

Instead:

/home/server/scripts/backup.sh

❌ Assuming cron knows your shell profile

Cron does not automatically load:

.bashrc

.profile

.zshrc

If required, source them manually inside your script.

Real-World Use Cases

This scheduling technique is particularly useful for:

• Planned maintenance windows
• Database migration jobs
• Temporary monitoring scripts
• Router firmware upgrades
• One-day log collection
• Limited-time promotional campaigns
• Cloud resource scaling during special events
• Security audits
• Disaster recovery drills

Final Thoughts

Cron is incredibly powerful, but many advanced scheduling requirements can be solved with a simple combination of cron expressions and shell conditions.

When you need "every 5 minutes, but only on a specific date and within a specific time range," there's no need for complex automation platforms. A few extra lines of shell logic can make your cron jobs precise, predictable, and production-ready.

Understanding these techniques can save time, reduce operational mistakes, and make your automation workflows significantly more reliable.