c - 时间转换

Question

我想计算 GMT 时间和当前时间的时差。为此，我使用 mktime 将 tm 时间(格林威治标准时间)转换为 time_t 格式。和当前时间使用 time() api。

struct tm = x;  time_t t1, t2; 
time(&t1);
/* here x  will get in GMT format */
t2 = mktime(&x);
sec = difftime(t2 , t1);

为了制作相同的时区，mktime() 是否会负责转换为本地时间？还是我需要显式添加 sec = difftime(t2 , gmtime(&t1);谢谢

Answer 1

是mktime转换为本地时间，请看man:

http://www.mkssoftware.com/docs/man3/mktime.3.asp

mktime() : convert local time to seconds since the Epoch

编辑:要计算两个日期之间的时差，您可以使用此

    time_t t1, t2;
    struct tm my_target_date;

    /* Construct your date */
    my_target_date.tm_sec = 0;
    my_target_date.tm_min = 0;
    my_target_date.tm_hour = 0;
    my_target_date.tm_mday = 20;
    my_target_date.tm_mon = 7;
    my_target_date.tm_year = 112; /* Date today */
    t1 = mktime (&my_target_date);
    t2 = time (NULL);
    printf ("Number of days since target date : %ld\n", (t2 - t1) / 86400); /* 1 day = 86400 sec, use 3600 if you want hours */