Cron expression to run every Sunday

Field breakdown

Minute 0, hour 0, day of month *, month *, day of week 0. Cron accepts 0, 7 and SUN for Sunday, so 0 0 * * 0, 0 0 * * 7 and 0 0 * * SUN are three ways of writing the identical schedule.

The reason both 0 and 7 exist is convenience for ranges. Since the week is numbered Sunday-first, "Friday to Sunday" would otherwise have to be written 5,6,0; with 7 available you can write the more natural 5-7.

Typical uses

• Weekly full backups, with incrementals on the other six days.
• Log compaction and archive rotation during the quietest hours of the week.
• Database maintenance: reindexing, vacuuming, statistics refreshes.
• Weekly digest emails — though those usually want a civilised hour, not 00:00.

Using it

# crontab, all equivalent
0 0 * * 0    /usr/local/bin/weekly-backup.sh
0 0 * * 7    /usr/local/bin/weekly-backup.sh
0 0 * * SUN  /usr/local/bin/weekly-backup.sh
@weekly      /usr/local/bin/weekly-backup.sh

The @weekly shorthand expands to 0 0 * * 0 exactly. It is convenient, but the explicit form documents itself better in a file someone else will read in two years.

Do not add a day-of-month restriction

Combining a weekday with a day of the month triggers cron's OR rule. 0 0 1 * 0 is not "the first Sunday of the month" — it is "the 1st of every month, plus every Sunday". Standard cron cannot express "first Sunday" at all. The workaround is a day-of-month range plus a guard:

0 0 1-7 * 0 /usr/local/bin/first-sunday.sh

That still fires on days 1 to 7 and every Sunday, because of the OR rule, so the reliable version tests inside the command:

0 0 1-7 * * [ "$(date +\%u)" = 7 ] && /usr/local/bin/first-sunday.sh

Here day-of-week is left as *, so only the day-of-month restriction applies, and the guard picks out the Sunday among days 1 to 7.

Variations