Question 1

What are the 5 fields in a cron expression?

Accepted Answer

A standard cron expression has five fields in this order: minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–6, where 0 is Sunday). For example, '30 2 * * 1' runs at 02:30 every Monday.

Question 2

What does */5 mean in cron?

Accepted Answer

A step value like */5 in the minute field means 'every 5 minutes'. The */n syntax repeats every n units, so '*/5 * * * *' runs every 5 minutes and '0 */2 * * *' runs every 2 hours on the hour.

Question 3

How do I run a cron job every day at midnight?

Accepted Answer

Use '0 0 * * *' — minute 0, hour 0, every day. To run daily at 3:30 AM use '30 3 * * *'.

Question 4

How do I run a cron job only on weekdays?

Accepted Answer

Set the day-of-week field to 1-5 (Monday through Friday). For example '0 9 * * 1-5' runs at 9:00 AM Monday to Friday.

Question 5

What is the difference between day of month and day of week?

Accepted Answer

If you set both, cron runs when EITHER matches (an OR), which surprises many people. To target a specific weekday, leave day-of-month as * and set only day-of-week.

* * * * *	Every minute
/5 * * *	Every 5 minutes
0 * * * *	Every hour, on the hour
0 0 * * *	Every day at midnight
30 3 * * *	Every day at 03:30
0 9 * * 1-5	09:00, Monday through Friday
0 0 1 * *	Midnight on the 1st of every month
0 0 * * 0	Midnight every Sunday

Crontab Generator & Explainer

Cron field reference