In trading, there is a fixed time period for the settlement of trades as per terms of contract. This time period is termed as Settlement Cycle.

For equity trades: Currently all trades are settled on T+1 settlement cycle. 

For derivatives/currency/commodities: Currently all trades are being mark to market at the closing price of contract and mark to market requirement are settled at T+1.

For arriving at the settlement day all intervening holidays, which include bank holidays, NSE holidays, Saturdays and Sundays are excluded.