A day corresponds to an actual rotation of the Earth, i.e., a day-night cycle. A year corresponds to an actual revolution of the Earth about the Sun, i.e., sea

A day corresponds to an actual rotation of the Earth, i.e., a day-night cycle. A year corresponds to an actual revolution of the Earth about the Sun, i.e., seasons. A week corresponds to...nothing. Four of them are a (very) rough estimate of the phases of the moon, but that's not something that really matters to anyone other than sailors nowadays.