On 28 July, 09: there was some problem at KSE server due to which, KSE had to suspend the trading session for little duration. During this suspended time period, all the orders that were placed: were cancelled. KSE has issued a notice which has all this detail mentioned in it.
Due to this suspension in trading, KSE decided to add 15 more minutes of trading session at the end of the day. That is why on 28th of July, 2009, the last trading session expired at 3:45 PM [local Pakistan Time], instead of the normal scheduled time of 3:30 PM.
So if you were trading at KSE on 28th of July, 2009 and you wondered why the last trading session got extended for 15 minutes: then now you know the reason.
