Welcome to TotalCalculators.com’s Leap Year Calculator! Use this simple and accurate tool to instantly check whether any given year is a leap year or not. Just enter a year and get the answer in seconds. What Is a Leap Year? A leap year is a year that has 366 days instead of the usual 365. The extra day is added to February, making it 29 days long instead of 28. This adjustment keeps our calendar year synchronized with the Earth’s orbit around the Sun — which actually takes about 365.242 days. Without this correction, the seasons and dates would slowly drift apart over time.