ISO 8601 includes the ISO Week date system, a numbering system for Weeks within a given year – each Week begins on a Monday and is associated with the year that contains that week's Thursday (so that if a year starts in a long weekend Friday–Sunday, Week number one of the year will start after that). ISO 8601 assigns numbers to the days of the Week, running from 1 to 7 for Monday through to Sunday.
Week is technically, except at Daylight Saving Time transitions or leap seconds,
1 Week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds