Nothing ruins fun like planning for it does. Scheduling leisure activities makes them feel more like work and less like fun. That's what researchers consistently found in a series of experiments.

The study didn't look at longer events like vacations, so honeymooners can relax. But when it comes to shorter term pleasures, from a latte to a movie, you might want to throw away your day planner.

“People associate schedules with work. We want our leisure time to be free-flowing,” says study co-author, Selin Malkoc, an assistant professor of marketing at Ohio State University's Fisher College of Business.

In one experiment, students were given a calendar filled with classes and extracurricular activities and asked to imagine that it was their own schedule for the week.

Half were then asked to make plans to go out for frozen yogurt with a friend two days in advance and add this activity to their calendar. The other half imagined running into a friend and going out for frozen yogurt immediately.

You might want to throw away your day planner.

Students who scheduled the excursion said it felt more like a commitment and chore than students who imagined an impromptu get-together.

But that's just thinking about having fun. What about actually having some?

The researchers had people pick a YouTube video that they wanted to watch. Some got to watch the video immediately, while others had to choose a specific date and time to watch the video and put in on their calendar.

Those who watched the video immediately enjoyed it a lot more than people who watched it on schedule later on. In fact, just setting a starting time for a fun activity is enough to make it less enjoyable, the team found.

It seems the devil really is in the details. And he doesn't want you to have fun.

But there's still hope for people who like leading a highly organized life. While people do seem to get less enjoyment out of precisely scheduled activities, this doesn't seem to happen when the activities are scheduled a bit more loosely — as proved by an experiment held during the week of final exams.

The researchers set up a stand on campus where they gave out free coffee and cookies. Before setting up the stand, they handed out tickets for students to pick up their coffee and cookies. Some tickets gave a specific time; others offered a two-hour window. While they were enjoying their freebies, the students filled out a short survey.

Those whose break was scheduled at a specific time enjoyed it less than those whose break had a two-hour window.

Malloc's take-home advice is simple: “Aim to meet a friend ‘this afternoon’ rather than exactly at 1 pm.”

The study appears in the Journal of Marketing Research.