Exporting/ importing changes expiration date of subkeys...

[gnupgpacker]

Hello,

importing to R2mail2 is working *without* changing expiration dates, if key
is exported from GnuPG-2.1.11...

"Converting-way":
Export GnuPG-1.4.23(GPGkeys/Win7) > Import GnuPG-2.1.11(Win7) > Export
GnuPG-2.1.11(Win7) > Import R2mail2(Android-8.1) > works faultless

>> Exporting (older) RSA keys should be independent from GnuPG version 1.4x
>> or 2.2x, isn't it?
> For each import/export operation you're asking about (both successes and
> failures), could you give the following information clearly:
>  * Are you exporting secret keys?
>    or exporting public keys?
RSA-4096 keypair secret + public
(1 main key C, 3 subkeys for S/A/E)

>  * where were the secret keys originally created? (on what program does
>    the original export happen?)
GPGkeys with GnuPG-1.4.23(Win7)

>  * which program is doing the import?
R2mail2(Android-8.1)

>  * does the program doing the import modify the OpenPGP certificate in
>    any way?
It seems to modify expiration date...

> it is not normal for the primary key to be marked as
> authentication-capable ("A").  If you have a tool that is doing that,
> please report back what tool that is, on what platform and what version!

Keys with this structure are created with GPGkeys (part of GPGshell for
Windows v3.78) and GnuPG-1.4.23, all included in Sebastians's GnuPG-Pack. 
http://www.rose-indorf.de/gnupgpack/ 

Example:
Geheimer Schlüssel ist vorhanden.
pub  4096R/C02860E1  erzeugt: 2018-11-13  verfällt: niemals     Aufruf: SCA
                     Vertrauen: uneingeschränkt Gültigkeit: uneingeschränkt
sub  4096R/37488B7B  erzeugt: 2018-11-13  verfällt: niemals     Aufruf: E
[ uneing.] (1). test <test at on.yourweb>
gpg>

In my lightweight opinion there must be issues while creating (SCA) and
exporting (date) those keys with GPGkeys/GnuPG-1.4.23(Win7)!?

Maybe time to change GnuPG setup to newer versions 2.1x or 2.2x...
But GPGrelay is needed...

Thanks for help and the constructive hint for exporting with GnuPG-2.x.
Pictures will be included in posts in the future :)

Best regards, Chris