A week is a time unit equal to seven days. It is the standard time period used for cycles of work days and rest days in most parts of the world, mostly alongside (but not strictly part of) the Gregorian calendar.
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).
The term "week" is sometimes expanded to refer to other time units comprising a few days, such as the nundinal cycle of the ancient Roman calendar.
"Week!" is the ninth single by Do As Infinity, released in 2001. The B-side, "Tsuredzure Naru Mama ni", is the only studio-recorded song by the guitarist Ryo Owatari, who also wrote the lyrics. The melody parallels that of song "Yesterday & Today". It was used as the theme song for the drama Yome wa Mitsuboshi.