In one scene when Tarek and Omar can't find May and sit down to talk, a Peugeot 505 appears in the background. Peugeot hadn't released their 505 model in 1975-76, the year at which the scene is supposed to happen.
Chevrolet M1008 Commercial Utility Cargo Vehicles - a militarized 5/4 ton version of the third generation Chevrolet C/K pickup - are seen in the movie, which was supposed to have taken place in 1975. The Chevrolet M1008 did not enter production until 1984.
On 13 April 1975, while class is in session, Tarek watches the ambush of the bus from the balcony of his school in Christian-dominated East Beirut. 13 April 1975 was a Sunday. Schools in East Beirut are closed on Sundays.