Okay, then I set the ticket to Testing.

Your fix is okay.

@werner: Shall we backport the fix to the gpgme-1.24-branch or do we just add a patch to gpg4win's gpg4win-4-branch and/or vsd-3.3-branch?

I have verified (by locally applying the change to a Gpg4win 4 build) that ifdef'ing-out the above hack for Windows builds fixes the display issue.

The capping of the date seems to be caused by this workaround/hack in gpgme's _gpgme_parse_timestamp

/* Fixme: We would better use a configure test to see whether
   mktime can handle dates beyond 2038. */
if (sizeof (time_t) <= 4 && year >= 2038)
  return (time_t)2145914603; /* 2037-12-31 23:23:23 */

The problem resulted from a split up key (one for encryption and one for signing) Resulting in no SMIME encryption key found for one recipient and thus falling back to OpenPGP.

The display in Okular is independent from Kleopatra, so dropping it in Kleopatra should be fine.
If a QES certificate is available, Okular should highlight and add a filter for them (which is currently not working, see T6632: Okular: Highlight / preselect "nonRepudiation" certificates for qualified signatures)

I currently have a slight preference to drop bold and go with normal font. Werner would be ok with that, too.

a) Here's a log anyway (ignore it, if decryption does always work):

@svuorela said, QES certs shouldn't be required to be on a smartcard.

Using an icon for QES certificates isn't that easy because we use an icon for smartcard certificates and any list item can have at most one icon. Moreover, QES certificates are very like stored on a smartcard (isn't that even a requirement?), i.e. an icon clash is basically guaranteed.

In T6632: Okular: Highlight / preselect "nonRepudiation" certificates for qualified signatures I had the impression, that some hint is useful for signing operations. Probably not so much in general.

Highlighting QES is mostly useful for Okular, I guess.
Maybe use a symbol with a pen? That should be self-explanatory.