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6th day of the month
six days
六日に届いた手紙を読んだ。
I read the letter that arrived on the 6th.
六日は予定が入っているから別の日にしよう。
I have plans on the 6th so let's make it another day.
来月の六日までにこの書類を提出してください。
Please submit this document by the 6th of next month.