Get current timestamp in milliseconds since Epoch in C++

This post will discuss how to get the current timestamp in milliseconds since Epoch in C++.

1. Using `std::chrono`

Since C++11, we can use std::chrono to get elapsed time since Epoch. The idea is to get the current system time with std::chrono::system_clock::now(). Then invoke the time_since_epoch() function to get the duration representing the amount of time elapsed since Epoch.

The following code example demonstrates its usage. It translates the duration to milliseconds and seconds using std::chrono::duration_cast. Note that C++20 standardized the time_since_epoch() function to Unix Epoch.

#include <iostream>

#include <chrono>

int main()

{

using namespace std::chrono;

uint64_t ms = duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();

std::cout << ms << " milliseconds since the Epoch\n";

uint64_t sec = duration_cast<seconds>(system_clock::now().time_since_epoch()).count();

std::cout << sec << " seconds since the Epoch\n";

return 0;

}

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2. Using `std::time`

The std::time returns the current calendar time encoded as a std::time_t object. It is defined in the header <ctime>. The following code example demonstrates its usage to get the number of seconds that have passed since the epoch.

#include <iostream>

#include <ctime>

int main()

{

std::time_t ms = std::time(nullptr);

std::cout << ms << " seconds since the Epoch\n";

return 0;

}

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That’s all about getting the current timestamp in milliseconds since Epoch in C++.

Get current timestamp in milliseconds since Epoch in C++

1. Using std::chrono

2. Using std::time

1. Using `std::chrono`

2. Using `std::time`