Most calendar years contain 365 days, but a leap year has 366. The extra day is added to February, creating 29th February, also known as ‘leap day’. Leap years usually occur every four years and help keep our calendar aligned with Earth's orbit around the Sun. The next leap year will be 2028.
Although leap years are a familiar part of the calendar, many people are unsure why they exist or how they affect everyday devices such as watches. In this guide, we'll explain the science behind leap years, answer common questions, and introduce G-SHOCK watches that automatically adjust the date, even during leap years, so you can always stay on schedule.
How do you calculate a leap year?
A simple way to determine whether a year is a leap year is to follow these rules:
● If the year is divisible by 4, it is a leap year.
● If the year is also divisible by 100, it is not a leap year.
● The exception is when the year is divisible by 400. In that case, it is a leap year.
Here are a few examples:
● 1900: Divisible by 100, but not by 400 = Not a leap year
● 2000: Divisible by 400 = Leap year
● 2028: Divisible by 4, but not by 100 = Leap year
● 2100: Divisible by 100, but not by 400 = Not a leap year
These rules are part of the Gregorian calendar and help ensure the calendar remains closely aligned with Earth's journey around the Sun.
Why do we have leap years?
Leap years help keep our calendar aligned with Earth's orbit around the Sun. While a standard calendar year has 365 days, Earth actually takes around 365.24 days to complete one orbit.
That small difference builds up over time and would gradually cause the seasons to shift away from their usual calendar dates. To prevent this, an extra day, 29th February, is added during leap years, usually every four years.
The Gregorian calendar also includes special rules for century years, helping keep the calendar accurately aligned with Earth's orbit over the long term.
What would happen without leap years?
Without leap years, the calendar would gradually drift out of sync with the seasons because Earth takes slightly longer than 365 days to orbit the Sun. While the difference is small each year, it builds up over time.
Eventually, seasonal events such as the start of spring or summer would occur on different calendar dates than expected. Leap years prevent this by adding an extra day to February every four years, helping keep the Gregorian calendar aligned with Earth's orbit and the seasons in their correct place.
When is the next leap year?
The next leap year is 2028. It will begin on Saturday 1st January 2028, and leap day will fall on Tuesday 29th February 2028.
Upcoming leap years include:
● 2028
● 2032
● 2036
● 2040
● 2044
● 2048
● 2052
Because leap years generally occur every four years, they are easy to anticipate. However, thanks to modern technology and advanced watch functions, you do not need to keep track of them manually when wearing selected G-SHOCK watches.
What happens if you are born on 29th February?
People born on 29th February are often known as ‘leaplings’. Although their birthday only appears on the calendar every four years, they age just like everyone else.
In years without a leap day, most leaplings celebrate on either 28th February or 1st March. Being born on a leap day is relatively rare, making it a unique birthday. Despite appearing only once every four years, 29th February is a recognised birth date, and people born on that day have the same legal rights and age-related milestones as anyone else.
How do watches account for leap years?
Many traditional watches require manual adjustment whenever a month contains fewer than 31 days. This means owners may need to correct the date display at the end of February and during other shorter months.
Modern G-SHOCK watches can simplify this process through advanced calendar technology. Depending on the model, automatic date adjustment may be supported by:
Full Auto Calendar
A full auto calendar is programmed with the correct number of days in each month and automatically adjusts the date, including during leap years.
Radio-Controlled Watches
Radio-controlled G-SHOCK watches receive time and calendar data from atomic clock transmitters. This allows the watch to automatically maintain highly accurate date information, including leap year corrections.
Bluetooth Smartphone Link-Compatible Watches
Bluetooth-enabled G-SHOCK models can synchronise with a smartphone via the Casio Watches App to receive accurate date and time information.
These features help ensure that your watch displays the correct date all year round, including the extra day that appears every leap year.
Recommended G-SHOCK Models That Automatically Adjust for Leap Years
If you want the convenience of automatic calendar adjustment, consider the following G-SHOCK watches:
GA-2100-1A1ER
The octagonal powerhouse that hit the scene in 2019 and became a collector's favourite. Its built-in calendar functions help reduce the need for manual date corrections.
GW-M5610U-1ER
A classic square G-SHOCK featuring Multi-Band 6 radio-controlled technology and a full auto calendar for effortless accuracy.
GA-B2100-1A1ER
A Bluetooth Smartphone Link-compatible model that automatically synchronises date and time information with your connected device via the Casio Watches App.
DW-6900RL-1ER
An updated version of the legendary 6900 series that was first released in 1995. Enjoy a bold design and iconic front-facing light with practical calendar functionality.
GA-110-1BER
The iconic overside analogue-digital model features advanced functionality and dependable everyday performance.
Never Miss a Leap Year with G-SHOCK
Leap years contain 366 days instead of the usual 365, with the extra day added as 29th February. This additional day helps keep the Gregorian calendar aligned with Earth's orbit around the Sun and ensures that dates remain connected to the seasons.
The next leap year will be 2028, bringing another leap day on 29th February. While traditional watches may require manual adjustment, selected G-SHOCK watches automatically account for leap years through full auto-calendar, radio-controlled, and Bluetooth synchronisation technologies.
Ready to find a watch that keeps up with every leap year?