It’s that time of year again, when students across the country get ready to spend serious money on college textbooks. But to get the best deals — on both buying books for the upcoming semester and selling your old texts — it may be worth paying closer attention to when you shop and sell.

A recent analysis by Extrabux, a cash-rebate Web site, found that the best time for students to buy and sell textbooks was from Aug. 20 to Aug. 26, as well as Jan. 7 through Jan. 13. And the worst time to do it was from Nov. 19 to 25th and April 9 through the 15 (which seems to coincide with spring break).

The reason is simple. It all traces back to the basics of supply and demand. The best time to buy textbooks, the analysis found, is when demand is high. “We found that the prices of many products sold online will decrease as the number of shoppers looking for those products increases,” said Jeff Nobbs, co-founder of Extrabux. “Online retailers/sellers want their prices to be as low as possible when there are the most consumers in the market looking for their products.”

He said the site looked at historical search trends for textbooks as well as price data through camelcamelcamel.com, which tracks price fluctuations from Amazon.com retailers.

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