 Welcome to English in a Minute. You already know there are seven days in a week. But what is the IT in this expression? Jonathan, I've been working on this project for the past 15 hours. I am so tired. 15 hours? I think it's time to call it a day off. I can't stop now, Jonathan. I must get this done. The other half of the project isn't due until next month. Really? Yeah. Call it a day, Anna. To call it a day means to finish doing something for now. This expression is usually used when talking about a person's work day. From the looks of it, Anna probably should have called it a day a few hours earlier. And that's English in a minute.