S&P 500 posts biggest monthly gain since October 2011 | Reuters

``A survey by payroll processing company ADP on Wednesday showed private sector employment rose higher than expected last month, but the government's measure of jobless benefits claims increased last week. "It's the calm before the potential storm. The uncertainty about tomorrow's numbers comes from that fact that we had a decent ADP report but the weekly claims were not so great," said Randy Frederick, managing director of active trading and derivatives for Charles Schwab in Austin, Texas.''