You do not only have the option of assigning time-limited permissions, but also give weekly recurring authorisations. In order to grant weekly recurring access permissions, just follow these steps:
Video Tutorial
Step-By-Step Guide

1. Tap + button
in details of the specific lock
2a. Type person's mail address and save it
to add a new smartphone user
2b. Select a person from the suggestion list
to add an existing smartphone user

3a. Add period
Deactivate the button Unrestricted and add a period.
3b. Switch the button to Repeat

3c. Pick date & time
You can choose multiple days for the same time period.
✔ Weekly recurring access permission is granted
If you want, you can add another period.