Meaning: to stop working for the day; to end work or a particular activity for the rest of the day
Why does it mean that?
"To call something" in this way means to declare or announce that something is over or stopped. For example, "They called the baseball game because of the rain." So, in this example, they canceled or stopped the baseball game because it was raining.
So, when we say, "Let's call it a day.", we are declaring that we should stop working or doing something for the day.
When do we use it?
We can use this after we have finished all our work.
- We have finished everything. Let's call it a day.
- We will never finish all of this today. Let's call it a day and finish the rest of the work tomorrow.
- I'm tired. I am going to call it a day.
We often use this expression by itself.
- Let's call it a day.
- We are all tired. Let's call it a day.
- Let's call it a day after we finish this.
- I want to call it a day.
- I will call it a day right after I finish this report.