The pre-open session is for a duration of 15 minutes from 9:00 am to 9:15 am.
It is broken down into two sub-sessions:
The order collection period of 8* minutes shall be provided for order entry, modification and cancellation. (* - System driven random closure between 7th and 8th minute). During this period orders can be entered, modified and canceled.
Order matching period starts immediately after completion of order collection period. Orders are matched at a single (equilibrium) price which will be open price. The order matching happens in the following sequence:
Eligible limit orders are matched with eligible limit orders
Residual eligible limit orders are matched with market orders
Market orders are matched with market orders.
All outstanding unmatched orders, after order matching period, are moved to the normal market retaining the original time stamp.
Like pre-market sessions, post-market sessions are only permitted for the equity segment. This session is open between 3:40 pm and 4 pm.
In the post-market session, the public can buy or sell orders in equity at the market price. However, note that if you place a market order it will be placed on the exchange at the closing price. Typically, the post-market session is not quite active. You can observe the stock movement from 3:40 pm to 4 pm by opening the watchlist.