The contract has an option for an additional year if both sides agree.
Gillet, 33, has 22 appearances with the Belgian national squad, scoring one goal.
Last season he played for French side FC Nantes scoring four goals in 57 matches, having previously played for clubs including Corsican side Bastia and Anderlecht in Belgium.
“I am very happy to be here. It was a long and difficult process but I am happy that I have signed and looking forward to my new teammates and for reaching our goals,” Gillet said.
Would you like to place a soccer bet? Click here to get started in 3 easy steps.