The best time is during their business hours, if you leave donations overnight good chances that the homeless people in the neighbor hood may do some ransacking.
During their business hours ONLY. They don't want you dropping things after hours because that is considered "Dumping". The don't take certain things like mattresses, box springs, tube televisions, chemicals, most car parts (ie, engines), and most building materials (ie, lumber).
During open hours.☺
Anytime, however, I'm pretty sure if it is after their normal business hours, you may have to leave your donation outside, on the side of the building.
During their business hours 8am-6pm
Thanks! Your answer is awaiting moderation.