I find it hard to appreciate these inventive types of API design. Something more traditional and boring, like Celery's crontab[1] or dateutils rrule[2] seem quite sufficient. For example:
I'm not sure why, given two equally flexible designs, we should choose the least expressive. The fact that cron is sufficient doesn't mean I don't still have to google how to run things every three hours every second Monday, for example.
[2]: https://labix.org/python-dateutil#head-470fa22b2db72000d7abe...