C++:
计算未来或过去的日期

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

int main() {
    using namespace std::chrono;

    //当前日期
    system_clock::time_point today = system_clock::now();
    //转换为tm结构
    time_t tt = system_clock::to_time_t(today);
    tm local_tm = *localtime(&tt);
  
    //打印今天的日期
    std::cout << "今天是: " << std::put_time(&local_tm, "%Y-%m-%d") << std::endl;

    //加上10天
    system_clock::time_point future_date = today + days(10);
    tt = system_clock::to_time_t(future_date);
    local_tm = *localtime(&tt);
  
    //打印未来的日期
    std::cout << "十天后是: " << std::put_time(&local_tm, "%Y-%m-%d") << std::endl;
  
    //减去30天
    system_clock::time_point past_date = today - days(30);
    tt = system_clock::to_time_t(past_date);
    local_tm = *localtime(&tt);
  
    //打印过去的日期
    std::cout << "三十天前是: " << std::put_time(&local_tm, "%Y-%m-%d") << std::endl;

    return 0;
}