THE Shenzhen stock exchange will change its trading hours, starting from August 9. The morning session will start at 9.30 am and end at 11.30 am. At present, the market opens at 9 am and closes at 11 am. For the afternoon session, the existing trading hours, from 2 pm to 3.30 pm, will be extended by 30 minutes, with the exchange open from 1.30 pm to 3.30 pm. Yesterday's announcement, issued by the exchange's new chief executive Xia Bin, did not give an explanation for the changes.