Re-setting a perpetual calendar that has exhausted its power reserve has traditionally been a bit of a faff. Vacheron Constantin thinks it has the answer.

by James Buttery

Re-setting a perpetual calendar that has exhausted its power reserve has traditionally been a bit of a nightmare. After all there are leap years, years, months, days, dates and time to consider. Of course, the advent of quick-set correctors simplified matters somewhat, but who carries that pusher tool around with them or, heaven forbid, might even be tempted to use the nib of a biro instead"
Wouldn?t it be better if, instead, your perpetual calendar was very unlikely to ever run down at all" That?s certainly the position that Vacheron Constantin has taken with the development of its incredibly innovative Traditionnelle Twin Beat Perpetual Calendar revealed at SIHH 2019 in Geneva.
Vacheron?s solution is a movement with two different balances, the Calibre 3610, which operates either at a high-beat 5Hz (36,000vph) frequency or an extremely leisurely 1.2Hz (8,640vph). The biggest noticeable difference between the two is the resulting power reserve; the Twin Beat can run at 5Hz for four days on a full wind, but use the pusher at eight o?clock to switch instantaneously over to 1.2Hz and the watch will run for 65 days. Yes, that?s more than two months on a single wind using the same single mainspring barrel.
Vacheron has previously created a 14-day movement, however it used four separate barrels to ...