Как осуществлять поиск файлов по дате?

#include <iostream>
#include <vector>
#include <ctime>
#include <iterator>
#include <algorithm>
#include <boost/filesystem.hpp>
#include <boost/date_time/gregorian/gregorian.hpp>
#include <windows.h>
 
namespace fs = boost::filesystem;
namespace gr = boost::gregorian;
 
namespace detail
{
// mode == 1: calc before d
// mode == 2: calc after d
// mode == 3: calc at d
void calc(const std::vector<fs::path>& path, std::vector<fs::path>& res, const gr::date& d, int mode)
{
    std::copy_if(path.begin(), path.end(), std::back_inserter(res),
                 [&](const fs::path& p)
    {
        auto t = gr::to_tm(d);
        double diff = std::difftime(fs::last_write_time(p), std::mktime(&t));
        return mode == 1 ? (diff < 0) : mode == 2 ? (diff >= 0) : (diff >= 0 && diff < 86400); // 86400 sec in a day)
    });
}
}
 
void created_before(const std::vector<fs::path>& path, std::vector<fs::path>& res, const gr::date& d)
{
    return detail::calc(path, res, d, 1);
}
 
void created_after(const std::vector<fs::path>& path, std::vector<fs::path>& res, const gr::date& d)
{
    return detail::calc(path, res, d, 2);
}
 
void created_at(const std::vector<fs::path>& path, std::vector<fs::path>& res, const gr::date& d)
{
    return detail::calc(path, res, d, 3);
}
 
void print(const std::vector<fs::path>& f)
{
    for (const auto& p : f) std::cout << p << "\n";
    std::cout << "\n\n-------------------------------------------\n\n";
}
 
int main()
{
    SetConsoleCP (1251); SetConsoleOutputCP (1251);
 
    fs::path directory_path("D:\\Temp");
    std::vector<fs::path> files{fs::recursive_directory_iterator(directory_path),
                fs::recursive_directory_iterator()};
    files.erase(std::remove_if(files.begin(), files.end(),
                               [](const fs::path &p){return !fs::is_regular_file(p);}
    ), files.end() );
 
    std::vector<fs::path> before, after, at;
 
    created_before(files, before, {2015, 1, 15});
    created_after(files, after, {2015, 1, 15});
    created_at(files, at, {2014, 12, 9});
 
    print(before);
    print(after);
    print(at);
}