time_t转换格式问题

Question

我正在尝试制作一个易于访问的TimeDate变量，但遇到转换问题。在time.h中，我将如何转换time_t的（自1/1/1970秒），到当前的本地时区（补偿夏令时如果适用），使：

time_t Seconds; 

变为：

struct TimeDate 
{ 
    short YYYY; 
    unsigned char MM; 
    unsigned char DD; 

    unsigned char HH; //Non-DST, non-timezone, IE UTC (user has to add DST and TZO to get what they need) 
    unsigned char MM; 
    unsigned char S; 

    char TZ[4]; //This can be optionally a larger array, null terminated preferably 
    char TZO; //Timezone Offset from UTC   

    char DST; //Positive is DST (and amount of DST to apply), 0 is none, negative is unknown/error 
}; 

在进程中不使用任何字符串文本（bar用于时区名称）（以保持其有效性）？这也考虑到了闰年。如果TimeDate可以转换回time_t，则为奖励。

Answer 1

C标准库（通过使用ctime在C++中可访问的），用于精确地为此目的（或gmtime对于UTC）提供localtime。在此之后，如果标准人员不能满足您的需求，那么您可以将生成的struct tm贴到您自己的结构中。

的一件事它不提供是时区本身，但你可以得到（在ISO 8601格式的偏移量）通过使用strftime与%Z和%z格式字符串

---

通过的方式举例来说，这里是一个演示这个动作的程序：

#include <iostream> 
#include <cstdlib> 
#include <ctime> 

int main(void) { 
    time_t t; 
    struct tm *tim; 
    char tz[32]; 
    char ofs[32]; 

    std::system ("date"); 
    std::cout << std::endl; 

    t = std::time (0); 
    tim = std::localtime (&t); 
    std::strftime (tz, sizeof (tz), "%Z", tim); 
    std::strftime (ofs, sizeof (ofs), "%z", tim); 

    std::cout << "Year:  " << (tim->tm_year + 1900) << std::endl; 
    std::cout << "Month:  " << (tim->tm_mon + 1) << std::endl; 
    std::cout << "Day:   " << tim->tm_mday << std::endl; 
    std::cout << "Hour:  " << tim->tm_hour << std::endl; 
    std::cout << "Minute:  " << tim->tm_min << std::endl; 
    std::cout << "Second:  " << tim->tm_sec << std::endl; 
    std::cout << "Day of week: " << tim->tm_wday << std::endl; 
    std::cout << "Day of year: " << tim->tm_yday << std::endl; 
    std::cout << "DST?:  " << tim->tm_isdst << std::endl; 
    std::cout << "Timezone: " << tz << std::endl; 
    std::cout << "Offset:  " << ofs << std::endl; 

    return 0; 
} 

当我在我的盒子运行它，我看到：

Wed Sep 28 20:45:39 WST 2011 

Year:  2011 
Month:  9 
Day:   28 
Hour:  20 
Minute:  45 
Second:  39 
Day of week: 3 
Day of year: 270 
DST?:  0 
Timezone: WST 
Offset:  +0800