C++ date and time

In this article, we will learn about the date and time formats in C++. There is no complete format in C++ for date and time so we inherit it from the c language. To use date and time in c++, <ctime> header file is added in the program.

<ctime>

This header file has four time-related types as follows -

Clock_t - It stands for clock type which is an alias of arithmetic type. It represents clock tick counts(units of a time of a constant with system-specific length). Clock_t is the type returned by clock()/.
Time_t - It stands for time_type. It represents the time that is returned by function time(). It outputs an integral value as the number of seconds elapsed when time passes by 00:00 hours.
Size_t - It is an alias for an unsigned integer type and represents the size of any object in bytes. Size_t is the result of the sizeof() operator which prints sizes and counts.
tm - The tm structure holds date and time in the C structure. It is defined as follows -

struct tm {
    int tm_sec; // seconds of minutes from 0 to 61
    int tm_min; // minutes of hour from 0 to 59
    int tm_hour; // hours of day from 0 to 24
    int tm_mday; // day of month from 1 to 31
    int tm_mon; // month of year from 0 to 11
    int tm_year; // year since 1900
    int tm_wday; // days since sunday
    int tm_yday; // days since January 1st
    int tm_isdst; // hours of daylight savings time
}

Date and time functions in c++

Name of the function	Prototype of the function	Description About the function
mktime	time_t mktime(struct tm *time);	This function converts mktime to time_t or calendar date and time.
ctime	char ctime(const time_t time);	It returns the pointer to a string of the format - day month year hours: minutes: seconds year.
difftime	double difftime ( time_t time2, time_t time1 );	It returns the difference of two-time objects t1 and t2.
gmtime	struct tm gmtime(const time_t time);	This function returns the pointer of the time in the format of a structure. The time is in UTC.
clock	clock_t clock(void);	It returns an approximated value for the amount of time the calling program is being run. The value .1 is returned if not available.
localtime	struct tm localtime(const time_t time);	This function returns the pointer to the tm structure representing local time.
time	time_t time(time_t *time);	It represents current time.
strftime	size_t strftime();	With the help of this function, we can format date and time in a specific manner.
asctime	char * asctime ( const struct tm * time );	The function converts the type object of tm to string and returns the pointer to that string.

Example to print current date and time

Below is the example to print the current date and time in the UTC format.

Code

#include <ctime> 
#include <iostream>


using namespace std;

int main()
{

    time_t now = time(0); // get current dat/time with respect to system

    char* dt = ctime(&now); // convert it into string

    cout << "The local date and time is: " << dt << endl; // print local date and time

    tm* gmtm = gmtime(&now); // for getting time to UTC convert to struct
    dt = asctime(gmtm);
    cout << "The UTC date and time is:" << dt << endl; // print UTC date and time
}

Output

The local date and time is: Wed Sep 22 16:31:40 2021

The UTC date and time is: Wed Sep 22 16:31:40 2021

The below code tells how to break the tm structure and to print each attribute independently with the use of -> operator.

Code

#include <iostream>
#include <ctime>
using namespace std;

int main()
{
    time_t now = time(0); // get current date and time

    cout << "Number of seconds since January 1,2021 is:: " << now << endl;

    tm* ltm = localtime(&now);

    // print various components of tm structure.
    cout << "Year:" << 1900 + ltm->tm_year << endl; // print the year
    cout << "Month: " << 1 + ltm->tm_mon << endl; // print month number
    cout << "Day: " << ltm->tm_mday << endl; // print the day
    // Print time in hour:minute:second
    cout << "Time: " << 5 + ltm->tm_hour << ":";
    cout << 30 + ltm->tm_min << ":";
    cout << ltm->tm_sec << endl;
}

Output

Number of seconds since January 1,2021 is:: 1632328553
Year:2021
Month: 9
Day: 22
Time: 21:65:53

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<ctime>

Date and time functions in c++

Example to print current date and time

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