The "model" option starts off close, but I just got into the year three "model" duna window, even though its supposed to be a 44 degree phase the alarm took it to a 34 degree phase. That drift isn't too bad as the delta V about 100 more to transfer. However each progressive window gets further off. And its not the calculator thats off, its the whole system has a different cadence now. The Alexmon calulator shows the same drift.