Every block provide a timestamp, but if the time is critical for you don't refer to this `timestamp` because a miner could modify it by about 900s you could use instead `block.number`. 

1- current block timestamp is returned by now :

e.g

    contract Test {
        function Time_call() returns (uint256){
            return now;
        }
    }

2- block Number is returned using block.number
  

     function Time_call() returns (uint256){
            return block.number; 
        }

to get the call time you could use the block.number and the [block time][1] (an avarage)


  [1]: https://etherscan.io/charts/blocktime