Mark Di Vincenzo, a journalist based in Newport News, Virginia, who interviewed hundreds of merchants and analyzed years of sales data and industry reports for his book Buy Ketchup in May and Fly at Noon: A Guide to the Best Time to Buy This, Do That and Go There (Harper). www.BuyKetchupInMay.com
Our guide to the best times to buy just about anything The prices of certain products fluctuate by 10% to…
