A leap year has 366 days.

闰年有366天.

《简明英汉词典》

A leap year occurs once every four years.

每四年才有一次闰年.

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A leap year is an intercalary year.

闰年是“插进来”的一年.

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This is a leap year.

今年是闰年.

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Add the joker, and it's the amount of days in a leap year.

如果再加上大王一张, 正好是闰年的天数.

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