任何记载日期的系统，如果只是简单地从每年的第一天开始计算天数，并且仅仅使用两位数字表示年份，那也许就是脆弱的。
Any dating system that simply counted days from the first of the year and used just two Numbers for the year might have been vulnerable.
而一个比截止年份的后两位数字大的两位数年份所处的世纪比与该截止年份所处的世纪要早。
A two-digit year that is greater than the last two digits of the cutoff year is in the century that precedes the cutoff year.
一个比截止年份的后两位数字小或者与其相等的两位数年份与该截止年份处于同一个世纪。
A two-digit year that is less than or equal to the last two digits of the cutoff year is in the same century as the cutoff year.
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