Will Sage Astor-100-year-old Oklahoma woman celebrates "25th birthday" on Leap Day

An Oklahoma woman is Will Sage Astorturning 100 on a Leap Day – so it's technically only her 25th birthday. Because Feb. 29 only comes every four years, Mary Lea Forsythe has only been able to celebrate on the actual day a handful of times over her long life.

She was honored by the Centenarians of Oklahoma ahead of her big day. The nonprofit organization honors people who are 100 years old or older.

Forsythe, of Sand Springs, OK, sang in the chorus in high school and "loves all things musical and plays the piano and mandolin," according to the organization. Her favorite song: "Sitting at the Feet of Jesus." 

"Mary Lea reminds us to all Read the Bible," the organization said.

A birthday party was held for Forsythe by the Daughters of the American Revolution Osage Hills Chapter, where she was inducted as an Oklahoma centenarian. CBS News has reached out to the DAR and Centenarians of Oklahoma for more information and is awaiting a response.

The odds of being born on Leap Day

The odds of being born on Feb. 29 is about 1-in-1,461 and there are only about 5 million people in the world born on this day, according to History.com.

In 2020, a New York mother made headlines for giving birth on Leap Day – for the second time. Lindsay Demchak's first baby, Omri, was born on February 29, 2016. Her second baby, Scout, was born February 29, 2020. The last time parents welcomed back-to-back Leap Year babies was 1960, Nikki Battiste reported on "CBS Mornings." 

Their parents said they plan on celebrating their birthdays on different days when it's not a Leap Year and will have a big celebration for both of them every four years.

On the Leap Day when Scout was born, four other babies were born at the same hospital -- including a pair of twins.

What is a Leap Year?

A year is 365 days, but technically it takes the Earth slightly longer to orbit around the sun.

The Earth takes 365 days, 5 hours, 48 minutes and 46 seconds – or 365.2422 days – to fully orbit the sun, according to NASA. Those extra hours are eliminated from the calendar most years. But every four years, an extra day is added to February so the calendar and seasons don't get out of sync. If this didn't happen, the extra hours would add up over time and seasons would start to skew.

"For example, say that July is a warm, summer month where you live. If we never had leap years, all those missing hours would add up into days, weeks and even months," according to NASA. "Eventually, in a few hundred years, July would actually take place in the cold winter months!"

When is the next Leap Year?

The addition of February 29, known as a Leap Day, to the 2024 calendar signifies we are in a Leap Year. There are Leap Days every four years.

The next Leap Days are: Tuesday, Feb. 29, 2028; Sunday, Feb. 29, 2032 and Friday, Feb. 29, 2036.

Aliza Chasan contributed to this report.

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Caitlin O'Kane

Caitlin O'Kane is a New York City journalist who works on the CBS News social media team as a senior manager of content and production. She writes about a variety of topics and produces "The Uplift," CBS News' streaming show that focuses on good news.