How does "is-uncertain-date" tests whether the given date variables contain approximate dates?

pureimagination

https://docs.citationstyles.org/en/stable/specification.html#approximate-dates

would result in “2005” (normal date) and “ca. 2003” (approximate date).

What I have to insert in the date field in zotero to get this output?

adamsmith

Zotero's own date field is quite limited, but dates entered via Extra can use a good share of ISO 8601
syntax.
I believe both
Issued:1776?
And
Issued: 1776~

work for uncertain dates