. . . my personal experience, HengHeng. I've had calendar problems with one of my cal 39 perpetuals before where the date would not transition over from the 30th to the 1st, but those weren't nearly as serious as the problem you're describing. Since the synchronization between date and month has been disturbed, your only safe option is to have it inspected by a G O service center. Btw, the problems I experienced with my first Karree perpetual were resolved under warranty, and once resolved, it ran perfectly for over three years without a hitch. Two of my subsequent cal 39 perpetuals have been flawless in terms of calendar operation, and the other exhibited the same 'sticking' problem as my first Karree, but the service center wasn't able to replicate the problem (!), so it was returned untouched (except for an extra scratch!!). Shortly thereafter, the watch suffered an indignity recorded several times on this forum, and was sent back for case repair and a full service; it has been a faithful companion ever since. Cordially, Art