Hedge fund managers are all afraid of one day each month -- the 15th. For the normal American this day doesn't signify much. But for fund managers this is the last day when hedge fund investors can redeem (withdraw) their money from hedge funds.

According to a New York Times article, credit funds and quantitative funds are expected to be the ones hardest hit by redemptions. The reason for this is simple to understand: many credit funds had subprime exposure and were hit hard due to drastic repricing in the subprime market and quantitative funds, notorious for group thinking, were hit hard when volatility spiked and funds were forced to begin closing their positions creating a death spiral in their positions.

Experts expect "hot money" such as funds of hedge funds based in Switzerland to be the first to withdraw money and move into less-leveraged funds according to the Financial Times.

In response to these fears, some managers are even prohibiting redemptions from their funds because it would force the funds to sell their positions at a steep discount. One such fund is Sentinel Management Group as the Associated Press reported here.

Today could be a make or break day for many hedge fund managers, especially those with a concentrated investor base.