Check this also and do the same experiment again.
But bare in mind, as mentioned by Nicolas: never turn the date with the crown backwards!
Also: the 5960 is not an anual calendar where you can adjust independently day, date and month, as far as I know.
You have to follow always a certain procedure, that should be in the manual.
On a side note: not to turn backwards over 0:00 or even 12:00 (!) applies also to any two hand dial watch from PP with caliber 240, although the date function is not a complication of the watch, but still of the MOVEMENT 240.
Hope it is a minor problem
Moritz
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