c++对时间的操作（chrono库）——字符创转时间，时间加减-Toy模板网

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1. 对时间的增加（小时）

#include <iostream>
#include <chrono>

int main() {
    std::chrono::system_clock::time_point now = std::chrono::system_clock::now();

    // 增加一小时
    std::chrono::hours oneHour{1};
    std::chrono::system_clock::time_point future = now + oneHour;

    // 减去一天
    std::chrono::hours oneDay{24};
    std::chrono::system_clock::time_point past = now - oneDay;

    std::time_t now_time = std::chrono::system_clock::to_time_t(now);
    std::time_t future_time = std::chrono::system_clock::to_time_t(future);
    std::time_t past_time = std::chrono::system_clock::to_time_t(past);

    std::cout << "当前时间：" << std::ctime(&now_time);
    std::cout << "加一小时后的时间：" << std::ctime(&future_time);
    std::cout << "减一天后的时间：" << std::ctime(&past_time);

    return 0;
}

输出结果：
当前时间：Tue Jul 11 19:48:45 2023
加一小时后的时间：Tue Jul 11 20:48:45 2023
减一天后的时间：Mon Jul 10 19:48:45 2023

字符串转标准时间然后对时间进行加减，然后转回字符串

#include <iostream>
#include <chrono>
#include <ctime>
#include <iomanip>
#include <sstream>

// 将字符串解析为时间点
std::chrono::system_clock::time_point parseTime(const std::string& timeStr) {
    std::tm tm = {};
    std::istringstream ss(timeStr);
    ss >> std::get_time(&tm, "%Y-%m-%d %H:%M:%S");
    std::time_t tt = std::mktime(&tm);
    return std::chrono::system_clock::from_time_t(tt);
}

// 将时间点转换为字符串
std::string formatTime(const std::chrono::system_clock::time_point& timePoint) {
    std::time_t tt = std::chrono::system_clock::to_time_t(timePoint);
    // std::tm* tm = std::gmtime(&tt); // 得到世界时间
    std::tm* tm = std::localtime(&time); // 得到当地时间
    std::ostringstream oss;
    oss << std::put_time(&tm, "%Y-%m-%d %H:%M:%S");
    return oss.str();
}

int main() {
    std::string timeStr = "2023-07-10 15:30:00";
    std::chrono::system_clock::time_point timePoint = parseTime(timeStr);

    // 加上一小时
    std::chrono::hours oneHour{1};
    timePoint += oneHour;

    // 减去一天
    std::chrono::hours oneDay{24};
    timePoint -= oneDay;

    std::string resultStr = formatTime(timePoint);
    std::cout << "加上一小时并减去一天后的时间：" << resultStr << std::endl;

    return 0;
}

转为一个函数

std::string turn(std::string time(1999-08-07 12:34:00))
    std::tm tm = {};
    std::istringstream ss(time);
    ss >> std::get_time(&tm, "%Y-%m-%d %H:%M:%S");
    std::time_t tt = std::mktime(&tm);
    std::chrono::system_clock::time_point timePoint = std::chrono::system_clock::from_time_t(tt);

    std::chrono::hours oneHour(more);
    timePoint += oneHour;


    std::time_t mm = std::chrono::system_clock::to_time_t(timePoint);
    //std::tm* tm2 = std::gmtime(&mm);
    std::tm* tm2 = std::localtime(&mm);
    std::ostringstream oss;
    oss << std::put_time(tm2, "%Y-%m-%d %H:%M:%S");
    std::string result = oss.str();

要将std::chrono::system_clock::time_point类型转换为字符串，你可以使用std::put_time函数或其他字符串格式化方法，例如使用std::strftime函数。

下面是使用std::put_time函数将std::chrono::system_clock::time_point类型转换为字符串的示例代码：

#include <iostream>
#include <iomanip>
#include <chrono>
#include <ctime>

int main() {
    std::chrono::system_clock::time_point timePoint = std::chrono::system_clock::now();

    std::time_t time = std::chrono::system_clock::to_time_t(timePoint);

    std::tm* tm = std::localtime(&time);
  
    std::stringstream ss;
    ss << std::put_time(tm, "%Y-%m-%d %H:%M:%S");
    std::string str = ss.str();

    std::cout << "转换后的时间字符串为：" << str << std::endl;

    return 0;
}

在这个示例中，首先获取当前时间的std::chrono::system_clock::time_point类型的时间点timePoint。然后，使用std::chrono::system_clock::to_time_t函数将时间点转换为std::time_t类型的时间。接下来，使用std::localtime函数将std::time_t类型的时间转换为std::tm*结构体指针，以便获取日期和时间的各个组成部分。

最后，使用std::put_time函数和std::stringstream来将时间转换为指定格式的字符串。std::put_time函数接受std::tm*结构体指针和格式字符串作为参数，可以将时间转换为指定格式的字符串。将格式化后的字符串存储在std::string类型的变量str中。

输出结果将是格式为"YYYY-MM-DD HH:MM:SS"的时间字符串。

请注意，这个示例中使用了本地时间（localtime）来格式化时间。你也可以使用其他时间标准或自定义格式来进行格式化。另外，确保包含了相关的头文件 <iomanip>, <chrono>, <ctime> 和 <sstream>。

2. 获取当前时间（标准时间格式2023 03:14 12:45）

// 获取当前时间
#include <chrono>
#include <iomanip>
#include <sstream>
#include <filesystem> 
std::string now_time()
{
    std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
    std::time_t tt = std::chrono::system_clock::to_time_t(now);

    std::tm* ptm = std::localtime(&tt);
    std::ostringstream oss;
    oss << std::put_time(ptm, "%Y-%m-%d %H:%M:%S");
    std::string result = oss.str();

    return result;
}
int main()
{
    std::string time_now;
    time_now = now_time();
    std::cout << time_now << std::endl;
}
结果：2023-07-18 16:45:58

3. 获取当前时间，对当前时间取整

// 获取当前整点的时间
#include <chrono>
#include <iomanip>
#include <sstream>
#include <filesystem> 
std::string now_time()
{
    std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
    std::time_t tt = std::chrono::system_clock::to_time_t(now);

    std::tm* ptm = std::localtime(&tt);
    ptm->tm_min = 0; // 去掉分钟 -------------------------
    ptm->tm_sec = 0; // 去掉秒----------------------------
    std::ostringstream oss;
    oss << std::put_time(ptm, "%Y-%m-%d %H:%M:%S");
    std::string result = oss.str();

    return result;
}
int main()
{
    std::string time_now;
    time_now = now_time();
    std::cout << time_now << std::endl;
}

结果：2023-07-18 16:00:00

3. 时间相减

方法一

// 时间相减
#include <chrono>
#include <iomanip>
#include <sstream>
#include <filesystem> 
int now_subtraction_time(std::string time_1)
{
    cout << "time1:" << time_1 << endl;
    std::tm tm = {};
    std::istringstream ss(time_1);
    ss >> std::get_time(&tm, "%Y-%m-%d %H:%M:%S");
    std::time_t tt = std::mktime(&tm);

    std::tm* ptm = std::localtime(&tt);
    int a = ptm->tm_hour;

    std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
    std::time_t tt2 = std::chrono::system_clock::to_time_t(now);
    std::tm* ptm2 = std::localtime(&tt2);
    std::ostringstream oss;
    oss << std::put_time(ptm2, "%Y-%m-%d %H:%M:%S");
    std::string result = oss.str();
    cout << "new:" << result << endl;
    int b = ptm2->tm_hour;
    int sub = b - a;
    return sub;
}
int main()
{
    std::string time1 = "2023-07-19 15:00:00";
    int a1 = now_subtraction_time(time1);
    std::cout << a1 << std::endl;
    std::string time12 = "2023-07-19 14:00:00";
    int a12 = now_subtraction_time(time12);
    std::cout << a12 << std::endl;
    std::string time13 = "2023-07-19 13:00:00";
    int a13 = now_subtraction_time(time13);
    std::cout << a13 << std::endl;
}
结果
time1:2023-07-19 15:00:00
new:2023-07-19 17:38:59
2
time1:2023-07-19 14:00:00
new:2023-07-19 17:38:59
3
time1:2023-07-19 13:00:00
new:2023-07-19 17:38:59
4

方法二文章来源地址https://www.toymoban.com/news/detail-561313.html

// 时间相减
// 时间相减
#include <chrono>
#include <iomanip>
#include <sstream>
#include <filesystem> 
double now_subtraction_time(std::string time_1)
{
    cout << "time1:" << time_1 << endl;
    std::tm tm = {};
    std::istringstream ss(time_1);
    ss >> std::get_time(&tm, "%Y-%m-%d %H:%M:%S");
    std::time_t tt = std::mktime(&tm);

    std::tm* ptm = std::localtime(&tt);
    int a = ptm->tm_hour;

    // 获取现在时间
    std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
    std::time_t tt2 = std::chrono::system_clock::to_time_t(now);

    double dTime = difftime(tt2, tt);  //返回值单位为秒

    double iHour = dTime / 60 / 60; //计算小时
    //double iMin = (dTime - iHour * 60 * 60) / 60; //小时的余数再除分钟的分钟数

    return iHour;
}
int main()
{
    std::string time1 = "2023-07-21 10:00:00";
    double a1 = now_subtraction_time(time1);
    std::cout << a1 << std::endl;
    std::string time12 = "2023-07-21 11:00:00";
    double a12 = now_subtraction_time(time12);
    std::cout << a12 << std::endl;
    std::string time13 = "2023-07-21 12:00:00";
    double a13 = now_subtraction_time(time13);
    std::cout << a13 << std::endl;
}
nowtime: 2023-07-21 14:19:00
time1:2023-07-21 10:00:00
4.31417
time1:2023-07-21 11:00:00
3.31417
time1:2023-07-21 12:00:00
2.31417