Bizarre day date change

[Pedro]

Hi everyone and hope everyone is OK. bought this watch in a joblot for a tenner (£10.00) so no complaints. The watch works fine but the date changes an hour forward every 24 hours. So if I cycle through the watch and it changes at 12, the next cycle it will be 1am, the next 2am etc. I also removed the hands, cycled the watch to the precise time of date change and then replaced the hands at the 12 O'clock position but the date started to change at the half past position with the same problem as above. The hands sit fine and are snug. Any ideas on what is going on? Many thanks and kind regards.

Pedro.

[JohnR725]

Just so I understand clearly first it's an hour off then you reposition the hands it's one half hour off?

As it's the calendar parts shall have to take the hands and dial off and see what's going on.

Then it's hard to go beyond this because which movement is this? But we could guess if the hands are actually tracking it's probably not a Canon opinion the problem perhaps. That takes us back to something to do with the the calendar parts which are under the dial unfortunately. Then we can't even look for a tech sheet if one even exists without a movement identification. But more likely have the watch hasn't been serviced in a long time that needs to be done.

[HSL]

Sounds like an interesting symtom, is it falling exactly 1 hour behind with every daychange or what?
A guess with that day date 70's model it would house an 718 movement.

[Pedro]

Hi, yes it is a 718 movement. Never come across this problem before. The watch is keeping great time but every day the date change changes an hour forward so one day will change at say 1am, the next 2am and so forth

[HSL]

Had to take a look how one of these loooked like, just happened to have a ORIS Twin Date lying around.

The day date share the same disk for the day date change which is driven through some gears by the hour wheel.
The hour wheel as you know is driven by the small pinion on the minute wheel, and the minute wheel is driven by the cannon pinion. This configuration should ensure the change of time and date to be synchronised by the time. 
So if the day date would be affected by the cannon pinion I would expect the time to be off too (check if the time slipps too). So if the time isn't affected this leaves us to the day and date disks, they either got loose from their gears or the day date jumpers are not correctly aligned.

Edited May 11, 2021 by HSL

[Pedro]

Cheers, the movement you have posted is identical to mine. As I am writing this the watch is still keeping excellent time but will keep an eye on it. Will have a look tomorrow and keep you posted, many thanks for your time, effort and advice, it is much appreciated.

Kind regards

Pedro.