Stock markets will open a half-hour earlier today.

No one, however, is predicting that a flood of new business will immediately greet the extension of Wall Street’s trading day to 6 1/2 hours. The move is another step toward round-the-clock trading but mostly is aimed at attracting new investments from Europe. In the West, however, many investors still may be in bed when markets open at 9:30 a.m. Eastern time, or 6:30 a.m. Pacific time.