Unfortunately the latest change to time-date.el reintroduced Bug#52209. 
I installed the attached patch to fix this, and to add some test cases 
mentioned in this bug report to help prevent the problem recurring. 
Also, this patch documents the new feature, and avoids 
overenthusiastically guessing the year to be 1970 when the date string 
lacks a year.

> (These functions were never really intended to support parsing dates
> like that -- only strict RFC822 date strings were originally supported,
> but it's become more DWIM as time has passed.

Yes, date-to-time has definitely ... evolved.

My understanding is that date-to-time's RFC822 parsing is present only 
for backward compatibility, and that we shouldn't attempt to enhance it 
(here, the enhancement would be pointless as the RFC822 parsing fills in 
the blanks anyway). So the patch I just installed adds the new feature 
only for the normal path taken, when not doing the RFC822 hack.


PS. Internet RFC 822 has been obsolete since 2001, and the Emacs code 
should be talking about RFC 5322 everywhere except when Emacs is 
explicitly supporting the obsolete standard instead of the current 
standard. And we should rename functions like rfc822-goto-eoh to 
rfc-email-goto-eoh, to help avoid confusion or further function 
renaming. But I digress....