Planet Fitness is offering free Leap Day-inspired workouts on Feb. 29 for everyone, including non-members, according to the gym.

“Planet Fitness is grateful to move together this Leap Day and reminds everyone that fitness is essential for our mental and physical wellness,” Sara Rooke, a spokesperson for Planet Fitness, wrote in a press release.

Since a Leap Year occurs almost once every four years, Planet Fitness wants to take full advantage of the extra calendar day by offering free workouts, according to the press release.

Almost every Planet Fitness location in Massachusetts, Rhode Island and New Hampshire will be open for people to work out on Feb. 29, according to the press release.

• Read More: Is 2024 a leap year? It sure is and this is what it means for your calendar

A leap year is a year that is one day longer than a regular calendar year. This happens almost every four years to ensure the calendar is aligned with Earth’s solar rotation. In 2024, February will have 29 days, rather than 28, MassLive previously reported.

Earth technically takes 365 days, 5 hours, 48 minutes and 56 seconds to orbit the Sun, according to airandspace.si.edu. But, the leftover time needs to be accounted for since it amounts to 23.2 hours every four years.

This is why our culture tacks an extra day to the end of February almost every four years. Without a leap year, months and seasons would occur at different times throughout the year, MassLive reported.

• Read More: Leap Year 2016: Are you working for free on Leap Year Day?

But, 23.2 hours isn’t a full day. If we leap exactly every four years, this would add an extra 44 minutes to our yearly calendar, shifting the months and seasons again, according to airandspace.si.edu.

Scientists have pointed to a common rule to align our calendar year with Earth’s rotation: If the year is divisible by 100, but not divisible by 400, a leap year is skipped, according to airandspace.si.edu.