Crontab Day of the Week syntax
:-) Sunday | 0 -> Sun
|
Monday | 1 -> Mon
Tuesday | 2 -> Tue
Wednesday | 3 -> Wed
Thursday | 4 -> Thu
Friday | 5 -> Fri
Saturday | 6 -> Sat
|
:-) Sunday | 7 -> Sun
As you can see above, and as said before, the numbers 0 and 7 are both assigned to Sunday. There are also the English abbreviated days of the week listed, which can also be used in the crontab.
Examples of Number or Abbreviation Use
15 09 * * 5,6,0 command
15 09 * * 5,6,7 command
15 09 * * 5-7 command
15 09 * * Fri,Sat,Sun command
The four examples do all the same and execute a command every Friday, Saturday, and Sunday at 9.15 o'clock.
In Detail
Having two numbers 0 and 7 for Sunday can be useful for writing weekday ranges starting with 0 or ending with 7. So you can write ranges starting with Sunday or ending with it, like 0-2 or 5-7 for example (ranges must start with the lower number and must end with the higher). The abbreviations cannot be used to define a weekday range.
You can also use day names like Mon for Monday, Tue for Tuesday, etc. It's more human friendly.
0 and 7 both stand for Sunday, you can use the one you want, so writing 0-6 or 1-7 has the same result.
Also, as suggested by @Henrik, it is possible to replace numbers by shortened name of days, such as MON, THU, etc:
0 - Sun Sunday
1 - Mon Monday
2 - Tue Tuesday
3 - Wed Wednesday
4 - Thu Thursday
5 - Fri Friday
6 - Sat Saturday
7 - Sun Sunday
Graphically, * * * * * command to be executed stands for:
| minute | hour | day of month | month | day of week | |
|---|---|---|---|---|---|
| (0-59) | (0-23) | (1-31) | (1-12) | (1-7) | |
| * | * | * | * | * | command to be executed |
Or using the old style:
┌────────── minute (0 - 59)
│ ┌──────── hour (0 - 23)
│ │ ┌────── day of month (1 - 31)
│ │ │ ┌──── month (1 - 12)
│ │ │ │ ┌── day of week (0 - 6 => Sunday - Saturday, or
│ │ │ │ │ 1 - 7 => Monday - Sunday)
↓ ↓ ↓ ↓ ↓
* * * * * command to be executed
Finally, if you want to specify day by day, you can separate days with commas, for example SUN,MON,THU will exectute the command only on sundays, mondays on thursdays.
You can read further details in Wikipedia's article about Cron and check a cron expression online with crontab.guru.