24 hours a day, 7 days a week.

There are 24 hours in a day, and 7 days in a week. 24/7 means all the time, non-stop and constantly. "I party 24/7" is an expression that suggests I never stop partying! Of course, if that we're true I would have no time to eat and sleep... It has become a common expression to mean constantly.

All day and night and the whole week.