Breguet MARINE ÉQUATION MARCHANTE 5887 Mode D'emploi page 29

5. Adjusting the date
E pushbutton III
English
Pushbutton III simultaneously adjusts the date C, as well as the
day of the week D, the month B and the year A, and the equation
of time disk B'.
Use pushbutton III to correct the date C to the day preceding the
desired day by passing over the end of the month.
In this example, the date is corrected from 1 December to 13
January after having passed over 31 December.