<Tr> <Td> (North American) </Td> <Td> Sunday </Td> <Td> 1 January </Td> <Td> 1st Saturday </Td> <Td> 1--7 days of year </Td> <Td> yes </Td> <Td> Canada, United States, India, Japan, Taiwan, Hong Kong, Macau, Israel, South Africa, most of Latin America </Td> </Tr> <P> The semiconductor package date code is often a 4 digit date code YYWW where the first two digits YY are the last 2 digits of the calendar year and the last two digits WW are the two - digit week number . </P> <P> The tire date code mandated by the US DOT is a 4 digit date code WWYY with two digits of the week number WW followed by the last two digits of the calendar year YY . </P> <P> The term "week" is sometimes expanded to refer to other time units comprising a few days . Such "weeks" of between four and ten days have been used historically in various places . Intervals longer than 10 days are not usually termed "weeks" as they are closer in length to the fortnight or the month than to the seven - day week . </P>

When was the days of the week created