Sell Rosh Hashanah, buy Yom Kippur...

Harry Schiller, one of the Street's more venerable technicians, called to note that the old trading tip really does have trading history behind it.

Over the last 40 years, Harry says, the average return has been minus 0.6 percent in the S&P 500 in the period between Rosh Hashanah and Yom Kippur. Remember, it's sell Rosh Hashanah, buy Yom Kippur, so that indicates it has worked.

Why does it work? Harry postulates that religious Jews are not supposed to be playing around with their stock portfolios before the high holy days. So the idea is to sell going into the holy days, and buy after.

Rosh Hashanah started last night at sundown, Yom Kippur is October 8.