The fiftieth World Environment Day was on June 5th, 2021.

2021年6月5日是第五十个世界环境日。

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In 1994, as we headed for the celebration of the fiftieth anniversary of D-day, several newspapers published a story on my father's war record, with a snapshot of him in uniform.

1994年，我们动身前往庆祝诺曼底登陆50周年，几家报纸刊登了我父亲在战时的服役记录，上面还有一张他穿军装的快照。

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The day marked the fiftieth anniversary of American women gaining the right to vote.

VOA: special.2009.10.18

Brown and Mr. Smith both teach a classroom of third graders who score at the fiftieth percentile on math and reading tests on the first day of school, in September.

NEWYORKER: Most Likely to Succeed