36 USC 109 - Fathers Day

(a) Designation.— 
The third Sunday in June is Fathers Day.
(b) Proclamation.— 
The President is requested to issue a proclamation
(1) calling on United States Government officials to display the flag of the United States on all Government buildings on Fathers Day;
(2) inviting State and local governments and the people of the United States to observe Fathers Day with appropriate ceremonies; and
(3) urging the people of the United States to offer public and private expressions of Fathers Day to the abiding love and gratitude they have for their fathers.