[Balgair]

> At this point you may start noticing a difference in dealer behavior: some of them are more open to negotiation that others. One of the reasons for that is that some of the cars are sitting on the lot for too long and they would like to get rid of them quicker to avoid burning money (keeping the car on the lot costs some amount each day due to insurance, parking space etc etc). This event is more likely in the end of the month or in the end of the calendar year (this post assumes that you cannot pick at what time of the year you buy a car. If you can choose, buy close to the end of December - there will be more inventory dealers will want to get rid of due to model line replacement).

(emphasis mine)

This part is buried in the whole document, but is probably the most important.

If you have some temporal wiggle room, go on the last day of the month. Not the second to last day, the very last day. Possibly after lunch if you can. You are going to get a much better deal.

Also, never buy a car at night.