TYPO3 Core

Currently, the scheduler accepts single numeric values only for representation of weekdays. Lower bound and included is 1, upper bound and included in range is 7. 1 means monday, 7 sunday.

However, even the currently reduced functionality is not fully compatible with an usual cron entry. Usally numeric zero is also allowed representing sunday.

man 5 crontab

Copying the cron entry weekday part in a local variable is by intention. It is not desired to manipulate the originally supplied cron entry part.
(issue imported from #M16321)