Because the Earth takes about 365.24 days to orbit the sun, these dates shift slightly each year, which is why we have leap years to keep them from drifting too far. 2. The Meteorological Seasons

(the longest and shortest days of the year). These dates vary slightly each year because the Earth takes about 365.24 days to orbit the Sun. Meteorological Seasons

Meteorologists and climatologists use a different system. They break the year into four three-month periods based on the annual temperature cycle and the Gregorian calendar. This makes record-keeping and data comparison much simpler. March 1 to May 31. Summer: June 1 to August 31. Autumn: September 1 to November 30. Winter: December 1 to February 28 (or 29). 3. The Hemispheric Difference