[Dovecot] offlineimap with dovecot: file-time is one hour in the future

I use offlineimap to sync my remote IMAP-server with my local IMAP-server (maildir format). But I don't understand this behavior: every new mail in the INBOX has a file-date which is one hour in the future. Is this 'normal'? Is this a problem of offlineimap? I tried this debugging (for dovecot): mail_executable = /usr/lib/dovecot/rawlog /usr/lib/dovecot/imap and this (for offlineimap): offlineimap -d imap,maildir,thread -l ~/offlineimap.log

But I can't find any helpful information in these files, which shows me what went wrong.

Has anyone a better technique or a hint how to find out what caused this (little) problem?

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Dieter Faulbaum