Get current day's duration in C++

main.cpp

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

using Timestamp = std::time_t;
using DayComponents = std::tm;
using Duration = std::chrono::duration<double>;

const auto dayComponentsFromTimestamp = std::localtime;
const auto timestampFromDayComponents = std::mktime;

Timestamp startOfADayFromTimestamp(Timestamp timestamp) {
    auto dayComponents = *dayComponentsFromTimestamp(&timestamp);

    dayComponents.tm_hour = 0;
    dayComponents.tm_min = 0;
    dayComponents.tm_sec = 0;

    timestamp = timestampFromDayComponents(&dayComponents);

    return timestamp;
}

Duration currentDayDuration() {
    using namespace std::chrono;

    auto clockNow = system_clock::now();
    auto currentTimestamp = system_clock::to_time_t(clockNow);

    auto startOfADayTimestamp = startOfADayFromTimestamp(currentTimestamp);
    auto clockStartOfToday = system_clock::from_time_t(startOfADayTimestamp);

    return clockNow - clockStartOfToday;
}


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

    auto duration = currentDayDuration();
    auto currentMinute = duration_cast<minutes>(duration).count();

    std::cout << "Current minute: " << currentMinute << '\n';
}