time_t转换格式问题

Question

我正在尝试创建一个易于访问的TimeDate变量,但我遇到了转换问题.在time.h中,如何将time_t(自1970年1月1日以来的秒数)转换为当前本地时区(如果适用则补偿夏令时),以便:

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
};

在此过程中不使用任何字符串文字(时区名称栏)(以保持其效率)？这也考虑到了闰年.如果TimeDate可以转换回time_t,则可以获得奖励.

Answer 1

C标准库(可通过使用C++访问ctime)提供localtime了完全相同的目的(或gmtime用于UTC).struct tm如果有一些原因导致标准的不足以满足您的需求,那么您可以将结果用鞋头敲打到您自己的结构中.

有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

举例来说,这是一个演示此操作的程序:

#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;
}

当我在我的盒子上运行时,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