Many ISU students probably don’t get excited about leap years, and some may not even realize that today marks a rare occurrence. But for one ISU student, today is a special occasion — it’s his “fifth” birthday.

Chris Zeiner, sophomore in aerospace engineering, is among the few people who have a leap-year birthday. He was born Feb. 29, 1980, and today is only the fifth time he has celebrated his birthday on the date he was born.

Zeiner typically does not get much attention for having a unique birthday, but lately his friends have been giving him a hard time about it, he said, especially since he’s “turning” five today.

“My friends say I’m really smart for my age,” he joked.

Though his official birthday only comes around every four years, Zeiner does not plan to celebrate his birthday in any special way this year.

“I can’t remember any times of doing anything differently during leap years,” he said.

Zeiner, who also shares his birthday with celebrities such as actor Dennis Farina and actor/model Antonio Sabato Jr., said he enjoys having a leap-year birthday.

“It’s unique; it’s different; [it’s] something that I can tell other people about,” he said.

During non-leap years, Zeiner usually celebrated on the weekend closest to his actual birthday or on “whatever date was easiest for my family.”

Russell Lavery, assistant professor in astronomy, said leap years do have a practical purpose.

“[Leap years serve] to keep the sky in the same position over a long period of time,” he said.

Lavery said the earth completes one revolution in 365.25 days. If an extra day were not added every four years, the position of the sun would change over time, since the earth does not take an equal number of days to complete one full revolution.

“We need leap years to keep the vernal equinox at the same date; otherwise, it would slowly move,” he said.

Lavery said no one person actually “discovered” the leap year.

“The ancient civilizations knew about the leap years because they had very good calendars and had leap months, instead of calling them leap years,” he said.

Lavery said ancient people had to decide how to account for the extra one-fourth of a day, so leap year was born.