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date (of a planned event, act, etc.); day
(number of) days
旅行の日にちはもう決まりましたか。
Have you decided the date of the trip?
日にちが経つのは本当に早いですね。
Time really flies, doesn't it?
締め切りの日にちを確認しておこう。
Let's check the deadline date.