I would think that Labor Day would be the next most likely time to see 0% offered. GM (and their competitors) use national holidays, Thanksgiving, Christmas, Memorial Day, Independence Day, etc., to introduce incentives like that.
And not to insult or burst your bubble, but be uber-thankful that your dad is buying you any vehicle, especially a new one. Who cares if it is 'cool' or not, it's a brand new car. And besides, there's nothing wrong with a Cobalt, especially a new one with a factory warranty.
