Difference Between Bikram Sambat and Ishwi Sambat: The Bikram Sambat is Based on Sideral Year which equals 365 days 6 hours 9 Minutes and 10 seconds. The Western Gregorian Calandar is Based on Tropical Year which equals 365 days 5 Hours 48 Minutes 46 seconds. So the difference is 20 Minutes and 24 seconds. The best way to convert Iswi Sambat to Bikram Sambat is to deduct AYANAMSA value for the particular Year. Ayanamsa for this year is 23 degrees, 53 minutes and 18 seconds. Hope this Helps You......... USername, will give you example later. Now I am out of station.... Hulaki Kaka.