HI Pankaj,
in addition to Nikunj, the no of days for Valuation is always calculated based on T+2 rule (maintained as default in Config). So in your first case when the Key Date is 30.11.2014 and Contract date is 28.11.2014, calculation of Swap will be 0 considering 28.11.2014+2 = 30.11.2014. If you try to valuate the same contract for say on 02.12.2014 you might get the results.
SAP Calculates No of Days like this :
“Key date of current valuation” – “date of last valuation” / “payment date” – “contract date + 2 days”
So in your case, 30.11.2014 - (28.11.2014+2){considering 30.11.2014 is the first Valuation date} / 27.01.2015 - (28.11.2014+2) = 0
Regards,
Nikhil