The time it takes for the Earth to complete one revolution around the Sun is approximately 365.25 days. This period is known as a tropical year or a solar year. However, to account for the slight fraction of a day, an extra day, known as a leap day, is added to the calendar every four years in what we call a leap year. In a leap year, the month of February has 29 days instead of the usual 28. This adjustment helps keep our calendar aligned with the Earth's orbital period around the Sun.