A leap year has a total of 366 days. Unlike a standard year, which has 365 days, a leap year contains an extra day added to the month of February, giving it 29 days instead of the usual 28. Leap years occur every four years to help synchronize the calendar year with the solar year, accounting for the fact that Earth's orbit around the Sun takes approximately 365.25 days. The rule for determining leap years includes some exceptions, such as years divisible by 100 not being leap years unless they are also divisible by 400. This system ensures long-term alignment of our calendar with the seasons.