They say timing is everything. When you are thinking about a new car, timing can save you thousands if you pick the right time of year — or cost you thousands if you don’t get the timing right. As the seasons pass, transaction prices can fluctuate with supply and demand. Automotive financing, cashback and leasing incentives change month to month, based on the time of the year. The inventory of new vehicles varies as model years change, and new cars, trucks, SUVs and minivans arrive in the market.

The absolute best month to buy is December, dealers say. To understand why December is the best time to buy a car, you need first to understand the process and the whys and wherefores. Car dealers and salespeople have quotas, lots of quotas. There are daily quotas, 10-day quotas and monthly quotas for the number of vehicles they have to sell. And there is a big goal — the annual quota. The end of the year is a busy time at dealerships because the very best deals of the year are offered on New Year’s Eve and New Year’s Day. The periods that manufacturers use to determine sales do not always coincide with calendar months.

The industry’s calendar for 2017, for example, had the sales month of December end Jan. 2, 2018. Your car purchase, this week, could determine the difference between the dealership hitting its annual sales goal and the salespeople receiving nice annual bonuses — or not. That’s why December, more specifically, the last week of the month, is the best time of year to buy a car. According to TrueCar, you can save an additional 8.3% off the price of a new car if you visit the dealership on New Year’s Eve.

Let’s say you were considering a used car going for $20,000. If you go in on New Year’s Eve, which is Tuesday, you stand to slash $1,660 just because you went in on the last day — and that’s in addition to other discounts offered. According to Mike Rabkin, owner and founder of From Car to Finish, the end of the month is great “because sales managers at dealerships have monthly quotas to hit and get compensated on whether they hit them or not.”

U.S. News and World Report notes that well-informed consumers are most likely to score great deals on new cars. The magazine provides buyers with all of the information they need, from learning about the buying process to choosing a new versus almost-new car and understanding financing options. Car loans are based on individual credit ratings. The higher one’s credit score, the lower the interest rate. The better the rate, the lower the monthly car payment. Buyers with established banking relationships can usually get better financing at their banks. Financing at a dealer’s business office means a point or two more on the interest rate regardless of a buyer’s creditworthiness.