I use “YYYY-MM-DD ddd” as date format in the title of my periodic notes.
For my tasks I usually don’t use due dates, I write my tasks in the according daily note instead.
So when I want to filter my tasks-query to all undone tasks before today, I have to refer to the filename and not to a due date… I assume I have to use “filter by function” instead of “before today”, like I did here, which leads to an error:
```tasks folder includes Periodic notes before today not done group by filename reverse ```
Can you please help me with the application of “filter by function”?
Thanks in advance,