DAYTON — We’ve been using the Gregorian calendar since 1582, here’s how it keeps our seasons and calendar on track. Hey it’s Storm Center 7 Meteorologist Ryan Marando.
You may have noticed that this year is not a leap year, meaning February has the regular 28 days. There’s a very important reason we have those leap days almost every four years though.
Many of us know one year is 365 days; however, our year is actually more approximately 365.2422 days. The Gregorian calendar, what we use now, updated the older Julian calendar to adjust the length of a year from 365.25 to 365.2425 to more closely represent our true year.
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The Gregorian calendar did this by adding another constraint for a leap year. Instead of just every four years, a leap year also will not happen on century years not divisible by 400. So 1900 was not a leap year, but 2000 was.
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This was so the calendar wouldn’t shift over time. Under the old calendar system, the start of the seasons drifted by 10 days or so before switching. If left unchecked, summer would start in December in several hundred years!