When did Jean-Bertrand Aristide become the dictator of haiti?

He was never a dictator, he was elected in open elections in 1991, after the previous hereditory dicatorship was overthrown by mass protests in the late 1980's. He served a 5 year term, and stepped down at the end of his elected term. In Haiti, you're allowed to run for election again, but not for consecutive terms, he ran again and was elected in 2001.

Getting elected and following your countries constitutional rules about terms in office, is what separates an elected president from a dictator.