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How to convert std::chrono::time_point to microseconds since epoch

If you have a std::chrono::time_point such as

timepoint_example.cpp
std::chrono::time_point<std::chrono::system_clock> timepoint = std::chrono::system_clock::now();

You can convert it to microseconds since epoch by first casting it to a chrono::duration using

timepoint_time_since_epoch.cpp
timepoint.time_since_epoch(); // Returns a duration

and then using std::chrono::duration_cast<std::chrono::milliseconds>(...).count() to convert it to microseconds since epoch and getting the number of intervals (= microseconds) in between epoch and the time point.

example.cpp
std::chrono::duration_cast<std::chrono::microseconds>(timepoint.time_since_epoch()).count()

Full example:

chrono_to_microseconds.cpp
#include <chrono>
#include <iostream>

int main()
{
    auto timepoint = std::chrono::system_clock::now();
    std::cout << "Microseconds since epoch: " <<
        std::chrono::duration_cast<std::chrono::microseconds>(timepoint.time_since_epoch()).count() << std::endl;
}

This prints, for example:

chrono_microseconds_example_output.txt
Microseconds since epoch: 1690755479946000

Here’s a simple snippet to convert std::chrono::time_point to microseconds:

timepoint_to_us.cpp
#include <chrono>
#include <cstdint>

int64_t to_microseconds_since_epoch(std::chrono::system_clock::time_point tp) {
    return std::chrono::duration_cast<std::chrono::microseconds>(tp.time_since_epoch()).count();
}

Usage example:

timepoint_usage.cpp
auto now = std::chrono::system_clock::now();
int64_t us = to_microseconds_since_epoch(now);
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