FILE: President Obama and first lady Michelle Obama gesture as they arrive to deliver remarks at a Christmas reception with service members at Marine Corps Base Hawaii in Kaneohe Bay, Hawaii December 25, 2015. REUTERS/Jonathan Ernst

How does President Obama celebrate on a day when he appears to have pulled off a double success on his most important foreign policy gamble?

By going to dinner at a fancy Washington restaurant.

Only it didn't appear to be about the Iran nuclear deal or prisoner release announced earlier in the day. The president and first lady Michelle Obama dined at Oyamel Cocina Mexicana on Saturday night for what reporters speculated was a birthday dinner for the first lady, who turns 52 on Sunday.

The Obamas "are having dinner with friends," the White House said in a note to the press pool that followed the president to the restaurant in the motorcade.

Located in Penn Quarter, Oyamel is run by award-winning chef Jose Andres, and was described by Washington Post food critic Tom Sietsema as a "rare source of memorable Mexican cooking in Washington."