Task: Question Answering
Input (English): Context : The Salonika Agreement (also called the Thessaloniki Accord) was a treaty signed on 31 July 1938 between Bulgaria on the one hand and the Balkan Entente--the states of Greece, Romania, Turkey and Yugoslavia--on the other. 
Question : What is the date when Salonika Agreement happened?
Output (English): 31 July 1938