Gianluca Coppola – By solar days, I suppose you meant calendar days between start and finish. Insert a Number1 column and you can use DateDiff(). DateDiff(“d”,[Start],[Finish]) returns the number of calendar days between Start and Finish but this function will return a value one less that what is expected. For example, for Start = 1 Jan, Finish = 1 Jan, this function will return 0 but we expect 1. So, in the formula add 1 to the returned value. Let me know if this helps.