Leaping to conclusions

By LINDA M. LINONIS

linonis@vindy.com

youngstown

Today is leap day.

Feb. 29 gets a special designation because that date appears on the calendar only in a 366-day leap year – and 2016 is one.

“It all comes down to numbers,” said Patrick Durrell, assistant professor in the physics and astronomy department at Youngstown State University and director of Ward Beecher Planetarium.

He explained that it takes the Earth 3651/4 days to rotate around the sun. The actual time it takes for the Earth to make one trip around the sun is 365.242189 days – or 365 days, 5 hours, 48 minutes and 45 seconds. That time adds up to what is termed a tropical year.

“But having a quarter day isn’t possible,” Durrell said. “To keep our calendar in step with the seasons, a day has to be added at some point.”

The day is added to February, the shortest month.

If Feb. 29 wasn’t included at various times, six hours would be lost every year. After a 100 years, the calendar would be off the mark by 24 days.

Durrell said adding the day at certain intervals “provides checks and balances” in the Gregorian calendar. If that wasn’t done, he said, eventually we would experience snow in July and warm weather in December.

The last leap year was in 2012.

Roman dictator Julius Caesar introduced the idea of a leap year, but the Julian calendar ended up with too many leap years, adding it every four years. The introduction of the Gregorian calendar in 1582 corrected that situation and devised a formula of three requirements. As noted on www.timeanddate.com, these three number situations must occur:

The year can be evenly divided by four.

If the year can be evenly divided by 100, it is not a leap year.

Unless the year also can be evenly divisible by 400.

So, while leap years don’t come regularly every four years, sometimes it looks that way. Upcoming leap years are 2020, 2024, 2028 and 2032, and 2100 will not be a leap year. Century years are not leap years unless they can be evenly divided by 400. So, 1700, 1800 and 1900 were not leap years, but 1600 and 2000, which are divisible by 400, were.