在C [重复]中使用Gettimeofday（）的日月和年算法

这个问题在这里已有答案：

• How can I convert seconds since the epoch to hours/minutes/seconds in Java? 6个答案

我需要作为实验室的一部分来设计计算当前月份日和年的方法 . 我将使用gettimeofday（）函数，它给出了自1970年1月1日以来的秒数 .

我知道有些函数会为我做转换，但设计要求是我创建自己的算法，将秒转换为几天和几年 . 我想要实现我的设计的方式是使用十二个月中的每一个的查找表和相应的天数 . 这个逻辑现在对我来说有点迷惑 .

棘手的部分是处理闰年 . 我知道1972年是自1970年以来的第一个闰年 . 自那一天起，闰年每4年发生一次 . 在这项任务中给我的暗示是，在几天之后的下一个最大周期是4年 . 因此，如果我模拟自1970年以来的天数1461（4年的天数），我知道我可以得到剩余的天数 . 在这一点上，我的逻辑逻辑迷失了 . 如果我在1461年将它分开，它只会告诉我已经过了多少4年 .

我想要实现的表格看起来像这样（我知道编码不是完全正确的，只是为了显示我的内容）：

struct Monthdays
{
int days;
char* Monthname[]
};

Monthdays lookupMonths[]
{
{31,"January"}
{28,"February"}
.
.
.

};

我试图找出如何使用天数或东西来创建一个适当的索引来走过这个“表”.........我希望在这里问这个是好的 . 我现在一直在努力解决这个问题或者几天......

这是我现在遇到的这个问题的代码非常低效 .

ExpandedTime* localTime(
                        struct timeval* tv,     // Pointer to timeval struct
                        ExpandedTime* etime     // '' '' to expandedtime strct
                        )
{
    tzset();                                    // Corrects for timezone

    int epochT = (tv->tv_sec) - timezone;       // Epoch seconds with
    int epochUT = tv->tv_usec;                  // epochtime microseconds
    int edays;                                  // Days since epochtime

    etime->et_usec = (epochUT/milli) % milli;   // Find the milliseconds

    etime->et_sec = epochT % 60;
    epochT /= 60;                               // Turn into minutes

    etime->et_min = epochT % 60;
    epochT /= 60;                               // Turn into hours

    if (localtime(&tv->tv_sec)->tm_isdst !=0)
        etime->et_hour = (epochT % 24) + daylight;      // Hours with DST correc
    else
        etime->et_hour = (epochT % 24);

    edays = epochT /= 24;                       // Turn into days

    etime->et_day = epochT;                     // Delete up to here
    etime->et_year = (epochT/365) + epochyear;  // Get the current year

    int trackyear;                              // Counter for years
    int trackdays = -1;                         // Subtracting janurary 1st
                                                // from days
   // This will determine if it is a leapyear and adjust days accordingly
    // from 1970 to current year (2013)

    for (trackyear = epochyear; trackyear < etime->et_year; trackyear++)
    {
        if (trackyear % leapy == 0)
        {
            trackdays = trackdays + 366;
        }
        else
        {
            trackdays = trackdays + 365;
        }
    }
    etime->et_day = edays - trackdays;

    int trackmonth = -1;                        // Counter for months
                                                // with offset to make
                                                // january = 0

    // This will give me the number of months for the buffer

    do
    {
        switch (trackmonth)
        {

            // Months with 31 days
            case 0:
            etime->et_day = (etime->et_day) - 31;
            break;

            case 2:
            etime->et_day = (etime->et_day) - 31;
            break;

            case 4:
            etime->et_day = (etime->et_day) - 31;
            break;

            case 6:
            etime->et_day = (etime->et_day) - 31;
            break;

            case 7:
            etime->et_day = (etime->et_day) - 31;
            break;
            case 9:
            etime->et_day = (etime->et_day) - 31;
            break;

            case 11:
            etime->et_day = (etime->et_day) - 31;
            break;

            // Months with only 30 days

            case  3:
            etime->et_day = (etime->et_day) - 30;
            break;

            case 5:
            etime->et_day = (etime->et_day) - 30;
            break;

            case 8:
            etime->et_day = (etime->et_day) - 30;
            break;

            case 10:
            etime->et_day = (etime->et_day) - 30;
            break;

            // Leap year month a.k.a Febuary

            case 1:
            if (trackyear % leapy)
            {
                etime->et_day = (etime->et_day) - 28;
            }
            else
            {
                etime->et_day = (etime->et_day) - 29;
            }

            break;

        }
        trackmonth++;

    }
    while(etime->et_day > 0);

    etime->et_mon = trackmonth - 1;
    // Reverts day offset from previous switch to
    // accurately represent the current day

    switch (etime->et_mon)
    {
            // Months with 31 days

            case 0:
            etime->et_day = (etime->et_day) + 31;
            break;

            case 2:
            etime->et_day = (etime->et_day) + 31;
            break;

            case 4:
            etime->et_day = (etime->et_day) + 31;
            break;

            case 6:
            etime->et_day = (etime->et_day) + 31;
            break;

            case 7:
            etime->et_day = (etime->et_day) + 31;
            break;

            case 9:
            etime->et_day = (etime->et_day) + 31;
            break;

            case 11:
            etime->et_day = (etime->et_day) + 31;
            break;

            // Months with only 30 days

            case  3:
            etime->et_day = (etime->et_day) + 30;
            break;

            case 5:
            etime->et_day = (etime->et_day) + 30;
            break;

            case 8:
            etime->et_day = (etime->et_day) + 30;
            break;

            case 10:
            etime->et_day = (etime->et_day) + 30;
            break;

            // Leap year month a.k.a Febuary

            case 1:
            if (trackyear % leapy)
            {
                etime->et_day = (etime->et_day) + 28;
            }
            else
            {
                etime->et_day = (etime->et_day) + 29;
            }

            break;
    }

    return etime;

}