完善我国抵押期限制度应从以下两方面着手：一是允许当事人自行约定抵押期限，但期限长短必须受一定限制，同时须规定约定期限经过登记后才能对抗第三人；

To perfect our mortgage term system, we can begin with the following two aspects: 1) allow the parties involved decide their mortgage term, but limited, and suitable to the third after registration;

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And then we calculate changes, the convention is understood with respect to what is the zero, right.

然后我们计算改变,这个约定就是用来规定零点的位置的。

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