::I apologize if I was unclear. The United States has no legislation in place that defines an official calendar. Using the IP editor's standard, there is no calendar at all in use in the United States, whereas there is a defacto standard that was inherited and hence, is customary. So, examining non-extant legislation would not serve in the case of the United States. If that fails in the case of the case of the largest population of English speakers in the world, on an English encyclopedia, it fails entirely. So, checking legislation cannot be a primary means of ascertaining the calendar in use in every nation.