Why can't Kleopatra (gpg4win) import my freshly-created key from another PC?

Question

I just created two new GnuPG keys on my linux box and then tried to import the public keys on my Windows 7 machine running gpg4win 2.1.0 with Kleopatra. However, I always get the message

Insgesamt bearbeitet:  2
Importiert:   0
Zertifikate ohne Benutzerkennungen:   2

or in English

Processed: 2
Imported: 0
Certificates without user IDs: 2

i.e. nothing is being imported.

What is the problem with these keys?? I just created them myself, minutes ago, and brought them over from the Linux machine using an USB stick. They both do have a user ID!

Answer 1

To find out more about the actual problem, don't trust Kleopatra's error message.

Running gpg2.exe from the command line, I got this:

gpg: key C0D3AFD2 was created 1810 seconds in the future (time warp or clock problem)
[...]
gpg: key C0D3AFD2: no valid user IDs
gpg: this may be caused by a missing self-signature
[...]
gpg: Total number processed: 2
gpg:           w/o user IDs: 2

So the signatures are being refused because their time/date is wrong!

Sure enough, the clock on the Linux machine which created the keys was set two hours into the future...