102 inches is legal, but that must include your side mirrors too. Wide body motorhomes have the body being 102 inches and the mirrors can stick out at least another foot on each side. How far you can stray from the interstate varies by state.
Sometimes, you need to know exactly how many years, months and days between two dates, in this situation, the following long formula may help you. 1. Years,  & DATEDIF(B1,B2,YM) &  Months,  & DATEDIF(B1,B2,MD) &  Days. Note: In the above formula, B1 indicates the start date and B2 stands for the end date, you can modify them as you need.
Or to calculate the date that is X days from a particular date, use the Days From Date calculator. Finally, if you want to choose a day in the week and count how many times it occurs in a given year, try out the How Many Days calculator. Enter two dates below to find the number of days between them. For best results, avoid entering years before 1753. Examples include 1959-11-27 or Nov 4, 2032.