YES Very Important!
I have been trying to filter by date => 20/2018
Because it’s not obvious from a devs point of view that only relative times are allowed.
ALSO - now I know that - Is there a list of the times available somewhere?
Yes.
However I’m not using the Pipedrive front end, purely through the API, and working from the available documentation.
So it is more difficult than should be.
The fact that filter JSON entered here /Filters/put_filters_id is different to the JSON required to Create/Update a filter through the API is confusing.
Anyway, It’s documented now, hopefully helping the next person.