The couple's 20th anniversary is on Wednesday, the same day the president will hold his first debate with Republican rival Mitt Romney.
"Go figure," the first lady said in a recent television interview.
The president says he and his wife have planned a belated celebration on Saturday.
The Obamas will at least spend their anniversary in the same city, a rarity as both are frequently in battleground states in the campaign's final weeks. Mrs Obama plans to be in the audience in Denver when her husband takes the debate stage.