Given a passage and a question, find the answer to the question based on the passage. The answer should consist of only one word that lies in the span of only one of the sentences in the passage.

Paragraph: A week is a time unit equal to seven days . It is the standard time period used for cycles of rest days in most parts of the world , mostly alongside -- although not strictly part of -- the Gregorian calendar .
Question: 1 week is equal to how many days
seven