In 2017, the (and often the best for negotiation due to low competition) was Halloween (October 31) . Conversely, the busiest day for shoppers was February 26 .

According to industry experts and 2017 year-in-review data, specific periods offered the best opportunities for deals: When Is the Best Time to Buy a New Car? - Edmunds

For high-level data on consumer behavior from that specific year, the by Cox Automotive provides the most comprehensive analysis of how and when people purchased vehicles. Key Timing Strategies for 2017