Today we celebrate Leap Year, the special time when February gets an extra day. The concept behind Leap Year has to do with keeping consistent time.
It takes the Earth approximately 365.242189 days – or 365 days, 5 hours, 48 minutes, and 45 seconds – to circle once around the Sun. But the Gregorian calendar year consists of only 365 days, so if we didn't add a leap day on February 29 nearly every four years, we would lose almost six hours off our calendar every year. After only 25 years, our calendar would be off by around 6 days.
By adding a day once every four years to our Gregorian calendar, we keep our measured time in alignment with the Earth’s revolutions around the sun. This extra day will be added every four years to our calendar until the year 2100—when we will need to skip the leap year to get the timing in sync again.
With all of this in mind, we can’t think of a better time to indulge in a calendar watch. There are annual calendars and perpetual calendars on the market and both are nice devices at different price points.
Essentially the annual calendar watch tracks the information of each month on the wrist, including offering day, date and month – taking into account months that are 30 and 31 days in length. However, this type of watch requires a resetting of the date every year at the end of February (which can be 28 or 29 days, depending on if it’s a leap year).
The annual calendar’s more exclusive and expensive sibling is the perpetual calendar. In addition to tracking all of the info the annual tracks, the perpetual also counts a few other dates, including leap year. With a perpetual calendar, the watch mechanism changes the date no matter how many days are in a month, taking into account leap years. Unlike annual calendars that need an annual adjustment, perpetual calendar watches will not need an adjustment until the year 2100 when, as mentioned we will skip a designated leap year.
Graphic courtesy: timeanddate.com