How much do you gain during a leap year?

Leap Years (every 4th year) are 1 day longer than normal years. This adjusts the Julian calendar to remain constant with the solar year, which is 365.25 days long. So we have three years of 365 days followed by one of 366 days. Smaller corrections mean that most century-ending years (1900, 2100) are not leap years, while those evenly divisible by 400 (e.g. 2000) are leap years as usual.