Tim Cook has tweeted a message in recognition of Memorial Day.

The day, which falls on the last Monday of May, honors the memory of those who died while serving in the armed forces. It is often marked by placing American flags or flowers on the graves of those who fell while serving in the military.

In November of last year, Cook tweeted a photo in honor of Veteran’s Day, which celebrates all American veterans, living and deceased. This included a photo of some of the veterans who work at Apple.

Memorial Day began as a grass-roots movement known as Decoration Day, when people would decorate the graves of those lost in the Civil War.

Photo: Parade

We honor the heroes who gave their lives for our freedom. They and their families have our eternal gratitude #MemorialDay

— Tim Cook (@tim_cook) May 29, 2017