Thanks,  what I see in my case is that urldate is ignored if either year or date field are present. Year or date are mandatory or the key contains the letters n.d. I still find seeing the year twice redundant and not consistent with how other entry types @book or @article display. 

On Thursday, September 22, 2022 at 11:26:11 PM UTC-7 Bastien Dumont wrote:
Here is a sample I got by exporting an item from Zotero and converting the CSL JSON file to BibLaTeX via Pandoc:

@online{PageWebSimple,
author = {Author, First Name},
title = {Title of the Web Page},
date = {2000-10-20},
urldate = {2019-07-20},
url = {http://placeholder.url}
}

Le Thursday 22 September 2022 à 03:03:21PM, Antonio Piccolboni a écrit :
> In what field am I suppose to enter that "June 8, 2021"? I tried year and
> urldate. The former is repeated twice verbatim, the latter ignored. Thanks
> On Thursday, September 22, 2022 at 1:45:43 PM UTC-7 Bastien Dumont wrote:
>
> Or to write a Lua filter, of course!
>
> Le Thursday 22 September 2022 à 08:44:17PM, Bastien DUMONT a écrit :
> > This is because the group ending with a dot contains the author-year form
> of the reference with the year only, whereas the second date is part of the
> full reference and would contain the full date if it were provided. The
> solution is to provide more information in order to get an output like this
> one:
> >
> > Doe, John. 2021. “A DSL That Is Concise and Fun.” Twitter. June 8, 2021.
> [1]https://web.archive.org/web/20211216060806/https://twitter.com/scalding.
> >
> > Le Thursday 22 September 2022 à 12:49:11PM, John MacFarlane a écrit :
> > > the CSL has
> > >
> > > <layout suffix=".">
> > > <group delimiter=". ">
> > > <text macro="contributors"/>
> > > <text macro="date"/>
> > > <text macro="title"/>
> > > </group>
> > > <text macro="description"/>
> > > <text macro="secondary-contributors" prefix=". "/>
> > > <text macro="container-title" prefix=". "/>
> > > <text macro="container-contributors"/>
> > > <text macro="edition"/>
> > > <text macro="locators-chapter"/>
> > > <text macro="collection-title-journal" prefix=", " suffix=", "/>
> > > <text macro="locators"/>
> > > <text macro="collection-title" prefix=". "/>
> > > <text macro="issue"/>
> > > <text macro="locators-article"/>
> > > <text macro="access" prefix=". "/>
> > > </layout>
> > >
> > >
> > > and I think the first date is coming from the "date" macro, while the
> second is coming from "access," which for web_page uses "issued" date.
> > >
> > > I don't know if this is a bug in the style or if there's some subtlety
> that's wrong in pandoc's CSL processing. Maybe a CSL expert can chime in
> here? Or try using Zotero with chicago-author-date.csl to see what it does.
> > >
> > > > On Sep 22, 2022, at 12:35 PM, Antonio Piccolboni <picc...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> wrote:
> > > >
> > > > Hi, I am producing pdf and epub from markdown. The bibliography is in
> biblatex. There is a problem with @online items in that the year is
> repeated twice in the output, be it pdf or epub. This is an entry:
> > > >
> > > >
> > > >
> > > > @online{scalding,
> > > > title={A DSL that is concise and fun},
> > > > url={[2]https://web.archive.org/web/20211216060806/https://
> twitter.com/scalding},
> > > > year={2021}
> > > > }
> > > >
> > > > And this is the result:
> > > >
> > > > “A DSL That Is Concise and Fun.” 2021. 2021. [3]https://
> web.archive.org/web/20211216060806/https://twitter.com/scalding.
> > > >
> > > > I am using the options --citeproc --bibliography biblio.biblatex
> > > >
> > > > Other item types look just fine.
> > > > Any suggestions? Thanks
> > > >
> > > >
> > > > Antonio
> > > >
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> References:
>
> [1] https://web.archive.org/web/20211216060806/https://twitter.com/scalding
> [2] https://web.archive.org/web/20211216060806/https://twitter.com/scalding
> [3] https://web.archive.org/web/20211216060806/https://twitter.com/scalding
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