This Day marks the twentieth anniversary of the International Day of Older Persons.

今天是国际老年人日二十周年纪念日。

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This year’s observance of the International Day Against Nuclear Tests marks the twentieth anniversary of the closure of the nuclear weapons test site at Semipalatinsk, Kazakhstan.

今年禁止核试验国际日正值哈萨克斯坦塞米巴拉金斯克核武器试验场关闭20周年。

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My wife has been on a cloud since I told her the other day I would spend my year-end bonus at the office to take us to Hawaii to celebrate our twentieth wedding anniversary.

我那天告诉我的妻子，我要把办公室发给我的年终奖金用来和她一起去夏威夷旅行，以庆祝我们结婚二十周年。 自从那天起，我太太一直很高兴。

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They celebrated the twentieth anniversary of the fall of the Berlin Wall in a peaceful revolution.

VOA: special.2009.11.14

The fiftieth anniversary of President Kennedy's inauguration will be January twentieth,two thousand eleven.

VOA: special.2010.10.29

Linda is coming up on the twentieth anniversary of the founding of her firm.

FORBES: How To Shatter The Public Accounting Glass Ceiling ?

Mills is celebrating the twentieth anniversary of Axis Records with a series of unique performances.

FORBES: Jeff Mills: Artist, Producer, DJ and Entrepreneur

This fall, Louboutin marks the twentieth anniversary of the company with a book about his career, to be published by Rizzoli.

NEWYORKER: Sole Mate