NEW YORK (CNNMoney.com) - Luck of the Irish?

Perhaps investors fear hung over or absent traders on St. Patrick's Day and want to get cracking ahead of time. Perhaps they shrink at the cackle of the approaching witches -- as in Friday's quadruple "witching," a quarterly options expiration that can cause volatility.

The day before St. Patrick's Day is often a good one for the bull.

Or maybe it's just a coincidence.

Whatever the reason, the day before St. Patrick's Day tends to be a good one for stocks, according to the Stock Trader's Almanac, the bible of stock market indicators, and Turov on Timing -- a daily and monthly newsletter about the market.

So Thursday should be a good day, if history is any guide. Of course, that's a big if.

Since 1953, as measured by the Dow industrials, the trading day before St. Patrick's Day has been good for a gain of 0.31 percent, according to the Almanac.

And while 0.3 percent is nothing to plan your retirement around, all in all, it's not bad.

St. Patrick's Day itself, like a hung over trader, is usually pretty flat. The Dow has risen an average of 0.14 percent on that day since 1953.

The day before many major holidays tends to be good, said Dan Turov, editor of "Turov on Timing," partly for the same reason that Friday tends to be more bullish than other days of the week.

That's partly because short sellers -- traders who have sold borrowed stock on bets that it will fall -- often look to buy back some of that stock to cover their positions and protect themselves before a break.

That process can help lift the overall market. The longer a break, the more likely the tendency, so it's especially true around the holidays.

Alternately, you could argue that hardened traders are feeling a bit warm and fuzzy about the holiday, or more likely, the prospect of vacation, and so they bid stocks up.

But St. Patrick's Day is not a market holiday. So what's the reason for the strength the day before?

It could be seasonal, the Almanac suggests -- mid-March is typically a good time of year for stocks, whereas late March tends to be tougher.

It could also be the impact of the first quarter's options expiration, which usually coincides with the week of St. Patrick's Day.

This week stock index options and futures and individual stock options and futures all expire simultaneously on Friday, which is also St. Patty's. The expirations have made for some volatile trading days in the past, though in recent years, that's been less so.

Turov, who spent the first 20 years of his career on Wall Street, said he thinks the reason is mostly about emotions. And libations.

"As people look forward to having fun, they're feeling better, and so markets perform better," Turov said. The more fun a holiday is, the more upbeat someone might feel about it. Therefore the day before St. Patrick's Day is a better day on Wall Street than, say, the day before President's Day.

In addition, there is the matter of some younger Wall Streeters being "hard drinking, hard partying young men," Turov said. This is a tendency that has not decreased over the years, he said, even as Wall Street has become run more by big institutions.

Two traders contacted for this story -- who asked not to be named -- conceded there was some "enthusiasm" for starting St. Patrick's Day celebrations the night before the holiday, which might add a certain urgency, or buoyancy, to trading the day before.

As to whether that "enthusiasm" would then lead to a fair number of hung over traders at their desks on St. Patrick's Day itself, the traders contacted by CNNMoney.com offered only evasive answers.

As to whether investors should avoid these hung over traders on St. Patrick's Day, well, the traders didn't want to say much about that either.

Like all market predictors, the St. Patrick's Day indicator has been proven wrong on several occasions.

In fact, it was wrong last year, when a mix of bad news out of General Motors and surging oil prices sent stocks lower on the two days prior to the holiday.

So don't bet the farm just yet.