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简述

由于C标准库<ctime>（或者<time.h>）中，只支持1970年之后的日期。因此我自制了一个可以将日期转化为从公元1年1月1日0点0分0秒开始所经历的毫秒数，或者反过来将毫秒数转化为对应日期。

如有错漏，还望指摘。

类定义

class time_struct {
   public:    time_struct() = default;    time_struct(long long ms, int base_year = 1);    long long ms_past_since(int base_year = 1) const;    std::string print() const;    bool is_leap_year() const;    bool check_validity() const;private:    long long ms_past_since_1() const;    void set_time_by_ms(long long ms);public:    short int year       = 1;    short int month      = 1;    short int day        = 1;    short int hour       = 0;    short int minute     = 0;    short int second     = 0;    short int milisecond = 0;};

毫秒数转日期

void time_struct::set_time_by_ms(long long ms){
       if (ms < 0)        return;    // milisecond    milisecond = ms % 1000;    ms /= 1000;    // second    second = ms % 60;    ms /= 60;    // minute    minute = ms % 60;    ms /= 60;    // hour    hour = ms % 24;    ms /= 24;    // How many 400 years are there    year = (int)(ms / 146097) * 400;    ms %= 146097;    // How many 100 years are there    // Since the last 100 years in a 400 years period    //     int num100years = ms / 36524;    if (num100years == 4)    {
           --num100years;        ms -= 36524 * 3;    }    else    {
           ms %= 36524;    }    year += num100years * 100;    year += (int)(ms / 1461) * 4;    ms %= 1461;    int num1years = ms / 365;    if (num1years == 4)    {
           --num1years;        ms -= 365 * 3;    }    else    {
           ms %= 365;    }    year += num1years + 1;    if (ms < 31)    {
           month = 1;        day = ms + 1;    }    else    {
           if (is_leap_year())        {
               ms = ms - 31 + 2;            month = (int)(ms * 12 / 367);            day = ms - month * 367 / 12;            day -= month ? 0 : 1;        }        else        {
               ms = ms - 31 + 3;            month = (int)(ms * 12 / 367);            day = ms - month * 367 / 12;            day -= month ? 0 : 2;        }        month += 2;    }}

以任意年为基准的毫秒数转日期

time_struct::time_struct(long long ms, int base_year){
       time_struct base;    base.year = base_year;    set_time_by_ms(ms + base.ms_past_since_1());}

日期转毫秒数

long long time_struct::ms_past_since_1() const{
       if (!check_validity())    {
           // TODO: log        // We assume LLONG_MIN is the error code        return LLONG_MIN;    }    int temp_month = month - 2;    int temp_year = year;    if (0 >= temp_month) {
       /* 1..12 -> 11,12,1..10 */        temp_month += 12;      /* Puts Feb last since it has leap day */        temp_year -= 1;    }    long long days = (long long)(temp_year / 4 - temp_year / 100 + temp_year / 400 + 367 * temp_month / 12 + day)        + temp_year * 365 - 337;    return ((((        (long long)(temp_year / 4 - temp_year / 100 + temp_year / 400 + 367 * temp_month / 12 + day)        + temp_year * 365 - 337        ) * 24 + hour        /* now have hours */        ) * 60 + minute      /* now have minutes */        ) * 60 + second      /* now have seconds */        ) * 1000 + milisecond; /* millisecond */}

日期转以任意年为基准的毫秒数

long long time_struct::ms_past_since(int base_year) const{
       time_struct base;    base.year = base_year;    return this->ms_past_since_1() - base.ms_past_since_1();}

检测是否是闰年

bool time_struct::is_leap_year() const{
       return ((year % 4) || (!(year % 100) && (year % 400))) ? false : true;}

检测日期有效性

bool time_struct::check_validity() const{
       if (year < 1)        return false;    if (day < 1)        return false;    switch (month)    {
       case 1:    case 3:    case 5:    case 7:    case 8:    case 10:    case 12:        if (day > 31)            return false;        else            break;    case 4:    case 6:    case 9:    case 11:        if (day > 30)            return false;        else            break;    case 2:        if (day > (is_leap_year() ? 29 : 28))            return false;        else            break;    default:        return false;    }    if (hour < 0 || hour > 23)        return false;    if (minute < 0 || minute > 59)        return false;    if (second < 0 || second > 59)        return false;    if (milisecond < 0 || milisecond > 999)        return false;    return true;}

打印日期

string time_struct::print() const{
       char buff[28];    sprintf_s(        buff,        "%04d-%02d-%02d %02d:%02d:%02d:%03d",        year,        month,        day,        hour,        minute,        second,        milisecond    );    return buff;}

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