BLACKSBURG -- It's usually not cool to get drunk on a Wednesday afternoon.

For all the efforts by parents and administrators to keep college students from drinking in excess, the social barrier that exists among students themselves, implying when it's not OK to drink, goes a long way toward controlling behavior. But it's a thin barrier.

One that is no match for "alcoholidays."

The term refers to days in which celebratory drinking is permitted, even expected. Suddenly those Wednesday afternoon drinkers don't seem so out of place if it's St. Patrick's Day or the week of Mardi Gras or Halloween, one of the most popular alcoholidays.

Steve Clarke, director of Virginia Tech's Alcohol Abuse Prevention Center, is studying the phenomenon.

While a few studies have looked at drinking trends on specific holidays, a complete treatment of alcoholidays is hard to find. Clarke is collecting data on Halloween and St. Patrick's Day to help the university create a program to address the issue.

"The best we can do is try to educate and make them aware of the situation," he said.

Without much hard data, many of the dates are anecdotal. But Clarke, a football season ticket holder who has been at the university since his days as a graduate student in the early 1980s, is confident that the list of days he has compiled is a good representation of days when students think it's OK to drink heavily.

"During the fall there's like six home football games. We have Halloween," he said. "And so that's seven weekends when we're going to see drinking go up. And there's typically only about 14 weekends a semester."

Clarke's list also includes the last day of classes for the semester, when students are given a day off, ostensibly to study. The weekend before classes begin for spring semester is big for parties, as are spring break and St. Patrick's Day. Some universities schedule spring break so it coincides with St. Patrick's Day to get students off campus during the holiday.

Even the weekend before Martin Luther King Jr. Day has become a big drinking weekend because students now have that Monday off, Clarke said.

Gary Walker, owner of Cabo Fish Taco in downtown Blacksburg, knows when finals begin and when each semester ends, and is willing to bet that owners and managers of other bars and restaurants in town have those days marked down as well.

"We know all those days because they affect our business," he said. "Bars like to take advantage of days when people are planning to party."

The restaurant, which opened in 2005, will have its third Halloween party this year. Walker, 35, doesn't remember Halloween being such a big bar night when he was a student, though he said there were plenty of house parties where students could drink.

Jillian Goodrich, president of Tech's ballroom dance club, is hoping a costume ball her organization is hosting the Friday before Halloween will serve as a popular option for students who want to celebrate the holiday without drinking. "I think that, in college in general, a lot of people feel they need to drink to fit in," the Tech junior said. "And when they dress up in costumes they feel like they can be somebody else."

Jon Peacock, a Tech graduate and general manager of Sharkey's, also thinks costumes are part of the reason Halloween has become such a big drinking night. The restaurant and bar, decorated with a "heaven and hell" theme will be ready to host costumed partiers on Halloween. Commemorative T-shirts, pint glasses and drink specials will also mark the event, one of the biggest nonfootball days of the year for Blacksburg bars.

And the bar will be stocked almost like there's a football game being played that day.

A study by Tech graduate students bears out the theory that the anonymity provided by costumes encourages some people to drink more. The study, published in May, shows average blood alcohol content of costumed revelers on Halloween to be .089. People who came as themselves averaged .058. The threshold at which someone is presumed drunk in Virginia is .08.

One of the good things about alcoholidays, Clarke said, is that bad things are less likely to happen when people drink to celebrate than when they drink for negative reasons, such as a breakup. Peacock said most of the crowds that come to Sharkey's to drink are well-behaved, with a couple of exceptions: When the Hokies lose or noon football games that become all-day drinking events.

As proved by the heavy drinking associated with football games, alcoholidays don't have to be actual holidays. Thursday nights have traditionally been big drinking nights at Tech and Tuesday nights are becoming popular as well, Peacock said.

It doesn't take much to create an alcoholiday, Clarke said.

"Students do that, they make things into holidays. Thursday. Let's party, let's celebrate," he said. "Once some students grab ahold of that idea -- that there's a reason to break out the alcohol and grab hold of it -- that's what happens."