Thanks ... unfortunately I already deleted this job. I now scheduled a new one and chose the monthly preset. - So lets see if something is happening on the coming tuesday or not. If not, my preset was likely wrong.
EDIT: I discovered what the 'problem' was. When typing zpool status. The output I was looking at was refering to the boot-pool, which has a scrub interval of 7 days and by chance those are tuesdays.