Determination of the day of the week ISO 8601. The day designated with 7 may also be counted as "0", by applying the arithmetic modulo 7, which calculates the remainder of a number after division by 7. Thus, the number 7 is treated as 0, 8 as 1, 9 as 2, 18 as 4 and so on. If Sunday is counted as day 1, then 7 days later (i.e. day 8) is also a Sunday, and day 18 is the same as day 4, which is a Wednesday since this falls three days after Sunday. The basic approach of nearly all of the methods to calculate the
Four-day week the state expected to save on operating costs such as electricity, heat, air conditioning, and gasoline for state-owned vehicles. Utah ended this practice however, in 2011, with the Utah Legislature overriding Governor Gary Herbert's veto of five-day work week legislation. Many local governments have had alternative schedules for many years. Public schools in Hawaii closed on 17 Fridays in 2010. Over 100 school districts in rural areas in the United States changed the school week to a four-day week; most also extended each school day by an hour or more. The changes were often made in order to save money