bug#51321: 29.0.50; date in modelines

[Eli Zaretskii]

> From: Niels Søndergaard <nisoni@algon.dk>
> Date: Fri, 22 Oct 2021 15:27:39 +0200
> Cc: Niels Søndergaard <nisoni@algon.dk>,
>  51321@debbugs.gnu.org
> 
> It’s correct that my format string use %a and %b, but the does NOT that yield 
> the locale-specific names, but English names
> 
> This is the locale setting on my iMAC 24”, it’s in Danish, but I guess that 
> it’s can be understood

I don't know what this means in terms of LC_* locale settings that
Emacs sees.  can some macOS expert please chime in and help me
understand where is the problem here?