It may be the closest thing to a sure shot on Wall Street.

Wednesday will be the day for investors to bet on a rise in the U.S. stock market, based on highly favorable odds instead of fundamentals like oil prices, corporate profits, interests rates, war and politics, according to a stock almanac followed by Wall Street pros.

While Wednesday is Bastille Day in France, in the United States it appears to be a day to go long the broad market. According to the 2004 Stock Trader's Almanac (search), July 14 scores the highest probability of the year -- better than 85 percent -- for a gain in the Standard & Poor's 500 index (search) based on more than 20 years of trading history.

The almanac said it determined the probability after examining decades of daily market moves, although investors should never forget Wall Street's favorite disclaimer: past performance is no indication of future results.

The almanac is standard issue for well equipped, professional traders. Assembled by the Hirsch family since 1967, it is a compendium of trading history, facts and figures, along with daily quotations from business and political achievers.

"My best assumption with the date is we get a nasty sell-off in the early part of July, and it is a combination of that and the tendency of the witching, the expiration day on Friday," said Jeffrey Hirsch (search), editor in chief of the almanac.

July 16 is the third Friday of the month, a day that typically brings increased volatility due to the expiration of certain options contracts.

"So it is a snap back (from a traditionally weak period for stocks) and one of the few shining spots of July," he said, noting that the day with the lowest likelihood of a rise in the S&P 500 is July 19.

The almanac said that Jan. 30 can claim the same odds for a rise in the S&P 500, based on trading data spanning from January 1982 to December 2002. It should be noted that the S&P 500 declined on Jan. 30, 2004, while it rose on July 14, 2003.

Hirsch added that with the rise on July 14 of last year, the probability of an S&P 500 gain this Wednesday has risen to 86.36 percent.

"That really is remarkable," said one veteran trader at a leading New York-area brokerage. He said the trend may be tied to stock buying related to second-half investing for retirement plans, such as 401(k)s.

But, he said, "everything regresses back to the norm."

When asked if he would bet the farm on the so-called Spiders an exchange-traded fund with underlying holdings that represent the S&P 500, another trader at a major New York brokerage said he would not.

"I have enough issues already," he said. He declined to elaborate.