如何在DateFormat中显示纪元？

import java.text.SimpleDateFormat;
import java.util.Date;

public class Main {
    public static void main(String[] args) {
        Date date = new Date();
        SimpleDateFormat dateFormat = new SimpleDateFormat("GG yyyy-MM-dd HH:mm:ss");
        String formattedDate = dateFormat.format(date);
        System.out.println(formattedDate);
    }
}

from datetime import datetime

date = datetime.now()
formatted_date = date.strftime("%G %Y-%m-%d %H:%M:%S")
print(formatted_date)

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

int main() {
    auto now = std::chrono::system_clock::now();
    auto time = std::chrono::system_clock::to_time_t(now);
    std::tm* tm = std::localtime(&time);
    
    std::cout << std::put_time(tm, "%EC %Y-%m-%d %H:%M:%S") << std::endl;
    
    return 0;
}