BibLaTeX entry year or date with text in it? The need to avoid a warning

Question

Is there a way to use the bibentry for year or date with for example date = {Around 171} or year = {Around 171} if the year and date of the work is historically not exactly known and to be precise with this fact? So that biblatex will neglect the "Around" and only use "171" for sorting? But of course prints the complete entry in the bibliography.

Or that something like year = {Vor 171 v.u.Z.} is possible, which means: "Before 171 B.C." (before 171 before Christ). This would be important for the greek and roman philosophers if one needs to quote them.

The warning looks like this:

WARN - legacy year field 'Around 171' in entry 'AurelDerWegzusichselbst' is not an integer - this will probably not sort properly.

Thanks for ideas.

Answer 1

Thank you to user Cicada who pointed in the comment to the biblatex Documentation to Table 5 where all of my 20 Warnings could be resolved with satifying results in the output.

Description of what I did for it: in the biblatex \usepackage[options]{biblatex} I set additionally to my option the two options: datecirca=true and dateera=secular (would be also possible christian or astronomical).

In the bibentries of the .bib file, I set:

date={171~} for output: "ca. 171"

date={-0349} for output: "350 v.u.Z.", and

date={-0045~} for output: "ca. 46 v.u.Z.",

with "v.u.Z." means the german secular abbreviation for "BC" (Before Christ), since I had loaded \usepackage[german]{babel}.

It is said in the documentation that these special settings only work with the date entry and not with the year. So I just replaced in my main .bib all year with date via copy-and-paste (respectively search and replace). And that solved the task.