If it feels like February is a bit longer this year – precisely one day longer – that’s because it is.

2024 is a Leap Year, meaning February gets an extra day this year. February, which is normally only 28 days long, will be 29 days this year with the 29th following on a Thursday. Leap Year occurs every four years, so the last one was in 2020 and the next will be in 2028 followed by 2032 and 2036.

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According to the Farmer’s Almanac, Leap Years are needed so that the calendar stays aligned with astronomical seasons.

Each orbit of the Earth around the sun takes about 365.25 days, even though the Gregorian calendar puts a year at 365 days. Without a Leap Year, the calendar would eventually get out of sync with the seasons and be off by 5 hours, 48 minutes and 45 seconds each year, the Farmer’s Almanac reported. After 100 years, the seasons would be off by 25 days.

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Adding the entire day every four years solves the problem created by the extra quarter day, giving a year 366 days instead of 365.

Or, as NASA explains:

“It takes approximately 365.25 days for Earth to orbit the Sun — a solar year. We usually round the days in a calendar year to 365. To make up for the missing partial day, we add one day to our calendar approximately every four years. That is a leap year.”

If you want to dive into the science you can do that here.

The math behind Leap Year can get complicated.

To be a Leap Year a year must:

• Be evenly divisible by 4
• Must be evenly divisible by 400
• But if the year can evenly divided by 100, it is not a leap year.

According to these rules, TimeandDate points out, 2000 and 2400 are leap years while 1800, 1900, 2100, 2200, 2300 and 2500 are not leap years.