A cron time is five fields: minute hour day-of-month month day-of-week. * means "every".
| Expression | Meaning |
|---|---|
0 4 * * * | every day at 04:00 |
30 3 * * * | every day at 03:30 |
0 */6 * * * | every 6 hours (00:00, 06:00, 12:00, 18:00) |
*/30 * * * * | every 30 minutes |
0 4 * * 1 | Mondays at 04:00 (0 or 7 = Sunday, 1 = Monday ... 6 = Saturday) |
0 14 * * 4 | Thursdays at 14:00 (Rust wipe day) |
0 4 1 * * | the 1st of every month at 04:00 |
0 4 * * 1,4 | Mondays and Thursdays at 04:00 |
The panel shows the fields as separate boxes: put 0 in minute, 4 in hour, * in the rest for a daily 04:00 run.
Mistakes
0 0 * * *is midnight, which is fine, but* 4 * * *runs every minute between 04:00 and 04:59. Always set the minute.- Day-of-month and day-of-week both set (
0 4 1 * 1) means "1st of month or Monday" in cron, which surprises everyone. Use one or the other.