All months have at least 28 days; however, February is the only month that typically has just 28 days, except during leap years when it has 29 days. This unique trait makes February distinct from the other months, which all contain either 30 or 31 days. Leap years occur every four years to align the calendar year with the solar year, as a complete rotation around the sun takes approximately 365.25 days. The addition of an extra day helps maintain the calendar's accuracy, ensuring that seasons remain consistent with their corresponding months over time, preventing the drift seen in a purely 365-day calendar.