As Nic will testify I've had 2 x C11 with the same problem.
AndyO...

: Hi Reinhold, one of technical folks on here will have more
: knowledge I'm sure, but I have had trouble like that in the past
: and it turned out it was something to do with the cal11 movement
: date wheel teeth wearing down. I would've thought however that
: the Silverstone was a cal12, which had an updated date wheel.
: Email Nic at heuer.boy@ntlworld.com , I'm sure he will be able
: to sort it for you.

: Congrats on the watch by the way, I think a Silverstone will be on
: my 'to buy' list very soon.

: Regards

: David H