The Breitling Watch Source Forums

May I know why one shouldn't change/update the time on breitling watch during this time ??
And is it only with breitling or with every automatic watch??
And how does the watch identifies if the month is that of 30 or 31 ???

Hello; I'll give you the quick answer. You can change the TIME as long as you advance, never reverse the time, that is the logic of always advancing the time and never going backwards. The DATE is what you do not want to change. This is due to the gears beginning to engage to advance the date. It is true with all automatics except the new in house movements, however should probably use current logic so as not to accidentally use on older mechanicals. 30 or 31 refers to week of manufacture. Hope this helps. Do a search for more in depth discussion on these subjects, sit back and enjoy your time here. It is very educational.

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911monty

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Lots of threads on those questions.......

With the majority of mechanical watches the date change is a gradual process to prevent a need for a huge amount of torque (relative to what is needed to run the watch) at one moment to change the date. The date changes through an additional wheel moving into the running train to change the date and that is in the process of moving in and out of the running train between about 9pm and 2am, hence the 8pm - 3am safety zone. Using the quick set date in that period can bend or strip teeth on the wheel that engages with the running train. Some movements have an instant date change where that isn't required, but it's less common. In Breitlings the in house movement has that as mentioned above, but it is not accurate to say that only the in house has it, one or two others have an instant date change as well - Cockpit as an example.

A regular watch doesn't know how many days are in the month, it assumes that every watch has 31 days and the user has to correct for months that have fewer. Only annual calendars / semi-perpetuals have allowances in the movement for days in the month and they have issues with February. A true perpetual can handle February / leap years as well. I wrote an article on perpetuals a few years back - http://www.breitlingsource.com/articles ... tual.shtml