Like many public figures, /twitter.com/billnye?lang=en"}}">Bill Nye “/www.youtube.com/watch?v=NnYgpihsONI"}}">The Science Guy” took a moment on Wednesday ― the 75th anniversary of the Pearl Harbor attacks ― to honor those who have served in the armed forces.

What many don’t realize, however, is that Dec. 7, 1941, is an important date in the Nye family’s history.

“It was the day my dad went missing, the day that lives in infamy,” Nye wrote on Twitter. His tweet features a picture of a 75-year-old copy of the Washington Evening Star newspaper that Nye said his grandmother had saved.

My grandmother kept this paper. It was the day my dad went missing, the day that lives in infamy. Honor those who have served. pic.twitter.com/SAG3KaXAJC — Bill Nye (@BillNye) December 7, 2016

In 1941, more than a decade before Nye was born, his father, Edwin Darby “Ned” Nye, was working as a contractor building an airstrip on the remote Pacific atoll of Wake Island.

“He said it was the greatest summer job he ever had,” Nye said of his father during a 2012 TED-Ed video lesson.

But on Dec. 7, Ned Nye’s world was turned upside down. Along with Pearl Harbor and many other Pacific targets, the Japanese bombed Wake Island. For two weeks, he and others fought back, managing to shoot down numerous enemy bombers, Nye explained in the TED-Ed. But on Christmas Eve, Ned and the others were captured.

Ned would spend nearly four years in a Japanese prisoner-of-war camp ― “longer than anyone else from the United States,” Nye said.

It was in the camp, where there was no electricity and watches were banned, that Ned reportedly learned to tell time using the shadow of a shovel handle.

Eventually, Ned made it out of prison and returned to the U.S.

“He left the bad memories of the camp behind, but his love for sundials stuck with him,” Nye wrote of his father in Popular Mechanics.

And that fascination eventually rubbed off on his son. In 2003, Nye helped design sundials for NASA’s Mars Exploration Rover project. Nye joked in the TED-Ed video that he’s developed SOD: “sundial obsessive disorder.”

“I think he’d be proud to know I helped put the first sundials on Mars,” Nye wrote of his dad.