Remember opening the doors of an advent calendar in preparation for Christmas?… What if your mother had woken you up during the emotionally charged lead up– maybe the day after Christmas Eve– saying “Oops! No Christmas this year, kids…it’s January 6th.”

To explain this strange but very possible occurrence, we have to go back in time. From 46 BC to 1582, Europe followed Julius Caesar’s ‘Julian’ calendar. But this calendar had miscalculated the length of the solar year by 11 minutes, and over hundreds of years it had fallen out of sync with the seasons. By the 16th Century, Pope Gregory XIII was less than impressed. He devised a new calendar to recalibrate the date to the seasons, with the help of Italian scientist Aloysus Lilius.

On the evening of September 2, 1752, millions of Europeans went to sleep – and woke up twelve days later. Since this awkward bit of time-travel, the Gregorian calendar has to be continuously fine-tuned, to maintain the correlation between the planets, the seasons, and ‘human’ time.
Enter the Perpetual Calendar…
Moser’s very first collection after the brand’s revival in 2005 included the Perpetual Calendar. A year later, this watch won the most prestigious prize in the watchmaking industry: the Geneva Watchmaking Grand Prix in 2006.

Not only did the Perpetual Calendar put H.Moser back on the map over a decade ago with its deceptively simple appearance and ingenious function (using a short central arrow hand to indicate the month) it has ‘stood the test of time’. To ensure the accuracy of this subtle complication year after year, we had to devise a way to incorporate all the finer quirks of Pope Greg’s Calendar. No sweat.
This included the discrepancy between the ‘year’ (made up of 365 days) and the actual length of the Earth’s rotation around the sun (365.242375 days). Adding an extra day every four years (a ‘leap’ year) would make up the difference… almost. But almost isn’t good enough when it comes to time. Or H.Moser watchmaking.
A finer calculation was needed. Leap years are those that can be exactly divided by 4…. unless the year can be exactly divided by 100, in which case it’s NOT a leap year… unless it can be exactly divided by 400, in which case it IS. Simple, right?

But don’t worry–that’s where the Perpetual Calendar shines. Beneath a deceptively clean, simple dial lies an intricately balanced mechanism that not only keeps time day to day, but year to year–even century to century.

So, if your descendants are fortunate enough to inherit an H.Moser, or if you live long enough to make it to the end of February 2100, you won’t have to remember any mind-numbing calculations. All you’ll have to do is pull out the crown and skip a day from the 28th February to the 1st of March. No leaping required.