SINGAPORE Exchange (SGX) said programming changes over the weekend led to a software error that affected end-of-day processing on Dec 1.
All post-trade online systems, including the client-accounting system, have been available since 6am on Wednesday, SGX said.
The stock market's pre-open routine will begin at noon, with the open set for 12.30pm. The market will close as normal after 5pm.
The Monetary Authority of Singapore (MAS) has called the disruption "unacceptable" and warned that it could take supervisory action if necessary.
"MAS has registered its disappointment and concerns with SGX over the delayed opening of its securities market caused by a software defect," an MAS spokesman said in a statement. "The lapse is unacceptable, coming within weeks of the recent power breakdown on Nov 5. MAS has instructed SGX board and CEO to do a thorough review to address the shortcomings that led to the lapse. MAS will not hesitate to take supervisory actions against SGX if necessary."