The findings? Students perform better when they space their study sessions rather than when they try to cram everything into their noggins during one sitting. But for those who must cram, timing is everything. According to the researchers, if you have only one date on which to study, choose a day that's closer to when you first learned the material than when you take the test—but not too close. For instance, if you have a French lesson on Monday and a quiz the following Monday, you should study on Wednesday for maximum retention. Tuesday is too early and Sunday is too late. (Procrastinators, find a different study.) "We find that the optimal time between two study sessions is roughly 10 percent of the time between the second study session and the final test," explains Hal Pashler, one of the lead authors. If you want to remember something for a year, wait about a month to review what you learned.