April 20th, 2011, 8:48 pm
30/360 - In this US day count convention, all full months are deemed to have 30 days and a full year 360 days. Let Y1 = year of the earlier date Y2 = year of the later date M1 = month of the earlier date (1 - 12) M2 = month of the later date (1 - 12) D1 = day of the month of the earlier date (1 - 31) D2 = day of the month of the later date (1 - 31)If D2 is the last day of February and D1 is the last day of February, then set D2 equal to 30.If D1 is the last day of February, then set D1 equal to 30;If D2 equals 31 and D1 is equal to 30 or 31, then set D2 equal to 30;If D1 is equal to 31, then set D1 equal to 30.Numerator = (Y2 - Y1)*360 + (M2 - M2)*30 + (D2 - D1).Denominator is always assumed to be 360 days per year.30E/360 - This is a European variation of the 30/360US rule which also assumes that all full months have 30 days and a full year 360 days. The difference between this day count and the US version is the treatment of certain dates in February.If D1 is equal to 31, then set D1 equal to 30.If D2 is equal to 31, then set D2 equal to 30.Numerator = (Y2 - Y1)*360 + (M2 - M2)*30 + (D2 - D1).Denominator is always assumed to be 360 days per year.30E+/360 - A variation of the 30E/360 rule. If D1 is equal to 31, then set D1 equal to 30 If D2 is equal to 31, then set D2 equal to 1 and increase M2 by 1.Numerator = (Y2 - Y1)*360 + (M2 - M2)*30 + (D2 - D1).Denominator is always assumed to be 360 days per year.Can you be a bit more specific about what you don't understand?