Simplify the following text for a Grade 9 native English-speaking person.
Original: From May 25 1964 to February 25 1986 , during the dictatorship of Francois and Jean-Claude Duvalier , the country had a different flag , in red and black , and divided vertically , not horizontally .
Simplified: From May 25 , 1964 , to February 25 , 1986 , Presidents FranÃ ois and Jean-Claude Duvalier returned to Dessalines 's black and red design .