停留期的计算，是以天为单位的，一般情况是从入境第二天开始。常见的中国签证停留期一般为30天，60天，90天，以及180天。而出入境查验的时候是严格按照天数计算的，所以不可以简单地解读为几个月或者半年。留心这一个小细节会让您在外出旅游的时候不至于因为逾期居留而受到行政处罚。

Many
passengers overlook the difference between 30 days and one month, and that often
causes overstaying. It is quite often when we meet with confused travelers at
the departure hall, saying: "Am I overstayed? I should be able to stay a month
here." But after verifying the visa, he or she would discover that the duration
is 30 days instead of one month. Unfortunately that month has 31
days.

Duration
of stay after entry calculates by days. It usually starts to count
from
the second day of entry. Generally, the duration of stay of
Chinese visas are 30 days, 60 days, 90 days and 180 days. And it can not be
simply interpreted as a few months or half a year. Mind this detail helps you to
avoid unnecessary administrative penalties during your stay in China.