Why is the UTC time in C++ 8 seconds ahead of the actual UTC time?

Asked May 13 '18 at 01:22

Active May 13 '18 at 05:26

Viewed 91 times

I have a simple function to print the current UTC time every second. Here is the code:

#include <iostream>
#include <thread>
#include <time.h>
#include <chrono>

using namespace std;

void printTime(){
    time_t now = time(0);
    tm *gmtm = gmtime(&now);
    char* dt = asctime(gmtm);
    cout << dt << endl;
}

int main(void) {
    while(true){
        printTime();
        this_thread::sleep_for(chrono::milliseconds(1000));
    }

    return(0);
}

My code prints a different time than the actual UTC time (compared to both my local machine and a website).

For example ...

My code prints Sun May 13 00:55:30 2018.

My local machine prints Sun May 13 00:55:22 2018 (I print it from a terminal with date -u).

Some website prints Sun May 13 00:55:22 2018 (same as my local machine).

What did I do wrong? Please help :(

[EDIT] I use Docker.

edited May 13 '18 at 05:26

asked May 13 '18 at 01:22

Hana Alaydrus

2,225
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19

My first instinct is leap seconds. – chris May 13 '18 at 01:26
Can you give details of your system, OS, compiler and timezone? I don't see the same problem on my system – M.M May 13 '18 at 01:32
Also see if the discrepancy occurs in `date; date -u` – M.M May 13 '18 at 01:34
do u remember to flush your output buffers? – Stephen Quan May 13 '18 at 01:41
@StephenQuan - the `<< endl` will do that. – selbie May 13 '18 at 01:52
Sorry! I forget to mention that I use Docker. Turns out if I exec to the Docker bash and try `date -u`, It will print ahead 10 seconds from the actual UTC time. – Hana Alaydrus May 13 '18 at 02:04
Thank you guys for the answer, turns out its docker container problem that the time usually out of sync and need some tweak. I will close this issue, thank you again! – Hana Alaydrus May 13 '18 at 02:13

Why is the UTC time in C++ 8 seconds ahead of the actual UTC time?

0 Answers0