KMail shows the verification result of a signature but it does not show the signature timestamp. It does not even show this information in the details. Enigmail shows this important information by default. Much better than showing this value by default would be to compare it to the non-crypto date mail header. If they differ by more than a few seconds then a warning should be shown. Another point: I have to admit that I didn't check this yet. But in case of PGP/Inline mails the timestamp and key ID of the body signature should be compared to those of the attachments. Reproducible: Always