What day is celebrated as flag day in the US?

On June 14, 1777 the Second Continental Congress passed a resolution that established our Nation's flag: Resolved: that the flag of the United States be made of thirteen stripes, alternate red and...

every year on June 14

The fourth of July. We capitalize the whole thing, The Fourth of July.

France has no 'flag day'. That celebration doesn't exist in France, and the national day in on the 14th of July to mark the storming of the Bastille and the beginning of the French revolution.

Isn't the answer in the very category in which you have placed this question? Independence Day is celebrated on the 4th of July!