Hello,
Unfortunately it's not possible to create recurring tasks. At the moment, only meetings can be set as recurring. We have plans for unifying the way Calendar events behave, but right now the idea is very rough. There are many angles the problem can be looked at and we want to make sure that if we decide to change the behavior again, it will bring desired results in all scenarios, so we can't really provide more details on that matter at the moment.
Kind regards,
Arek