Generating a short string containing the time with strange results - c++

Question

I have a function which creates a std::string with the time in it in cpp as follows:
#include "msattime.h"
#include <QTime>
#include <stdio.h>
#include <iostream>
std::string msattime::getTime(){
QTime t = QTime::currentTime();
std::string s;
char hours[5];
char minutes[5];
int min = t.minute();
itoa(t.hour(), hours, 10);
itoa(min, minutes, 10);
if(min < 10){
minutes[1] = minutes[0];
minutes[0] = '0';
minutes[2] = '\0';
}
s.clear();
s = s.append(hours).append(":").append(minutes);
return s;
}
This works just fine is the time in the minutes field does not contain a zero in the tens position. I changed my system time to many different values and used cout to print the string that resulted from this function. This table shows the input on the left and the output on the right.
9:19 AM || 9:19
11:20 AM || 11:20
10:20 PM || 22:20
5:24 PM || 17:24
5:00 PM || 17:00[
7:03 PM || 19:03┐
11:04 PM || 23:04!! (This is supposed to be a single character double bang)
12:09 AM || 0:09┌
The values for the hour are all correct. At some point there will be an option for the user to change the display format to 12h but for now there are no errors in those results. The only error is in the minutes place where there is an extra character added after the string. I don't get any errors when I print the string to the terminal so that suggests that it is null terminated at some point.
I have a display routine for a low resolution black and white lcd display that will print a value with center alignment. If I print this string with that alignment it gets forced to left alignment. The center printing function calculates a starting position based off of string length and then begins printing from that position. Because this string is forced to left alignment when printing using this method there is reason to believe that it is very very long.
Does anyone have any ideas about why this might be happening to me or have a suggestion for another get time function that with the same or similar output?
Environment:
Window 7 Pro w/ SP1 64bit
QT Creator IDE
QT 5.1.1
MinGW 32bit compiler with C++11 compliance turned on

Answer 1

I'd use strftime to do the formatting. Code would be something like this:
std::string getTime(){
time_t now = time(NULL);
struct tm *t = localtime(&now);
char buffer[16];
strftime(buffer, sizeof(buffer), "%H:%M", t);
return std::string(buffer);
}
If you're using multiple threads, you may want switch to from localtime to localtime_r instead.

Answer 2

The QTime class provides toString. This should be enough:
return QTime::currentTime().toString("h:mm").toStdString();
I also would recommend to use QString until you really need std::string.