Meaning: （1日の仕事等を）切り上げる、何かをするのをやめる
For Example:
‣ We have made enough process on this project today. I'm feeling tired now, let's call it a day.
今日はこのプロジェクトを十分進めることが出来たわね。私疲れちゃったわ。今日はこの
辺にしましょう。
‣ Okay. I've studied for 2 hours after cramming school. I think I'll call it a day today and go to sleep.
ふぅ、塾の後に2時間勉強したわ。今日はもう終わりにして寝よ。
Synonym:
to bring to the end, to stop doing