The **`mktime`** function, defined in the `time.h` header file converts the value of time in it to the corresponding local time zone in the form of a `time_t` object.

It performs when given an object of type `tm` as an argument.


# Function syntax

# Parameters
`mktime` takes a single, mandatory, argument as a parameter, which is a pointer to a `tm` structure. Following is the definition of the `tm` structure:  


| Elements        | Represent                    |
|-----------------|----------------------------|
| **`tm_sec`**   | Seconds passed in a minute |
| **`tm_min`**   | Minutes passed in an hour  |
| **`tm_hour`**  | Hours passed in a day      |
| **`tm_mday`**  | Months passed in a year    |
| **`tm_mon`**   | Months passed in a year    |
| **`tm_wday`**  | Days passed in a week      |
| **`tm_yday`**  | Days passed in a year      |
| **`tm_year`**  | Years passed since 1900    |
| **`tm_isdst`** | Daylight saving hours      |


# Return value
The `mktime` function returns:

* An `mktime` object corresponding to the time in the `tm` object sent as parameter for successful execution.
* A "-1" if there was an error in execution.

# Example

In the following example, we first make and populate a `tm` object fed as argument to the `mktime` function. Afterward, we used the `ctime` function to generate a printable string (of format **Www mmm dd hh:mm:ss yyyy**) corresponding to the value stored in our the `time_t` variable populated using the `mktime` function:

#include<stdio.h>
#include<time.h>

int main()
{
  // variable to store the return of the mktime function
  time_t  my_time;
  // variable to give mktime as parameter
  struct tm mytm;

  // populating the tm object
  mytm.tm_year = 2021 - 1900; // 2021
  mytm.tm_isdst = 0; // day light saving set to 0
  mytm.tm_mon = 1; // January
  mytm.tm_mday = 0; // Sunday
  // setting the time as 00:00:00
  mytm.tm_hour = 0; 
  mytm.tm_min = 0; 
  mytm.tm_sec = 0;


  my_time = mktime(&mytm);

  //  converting the time in my_time into a reader 
  // friendly string of format Www mmm dd hh:mm:ss yyyy 
  printf(ctime(&my_time));

  return 0;
}

The result of the code shows us that the values we put into the `tm` object were successfully stored in our `time_t` variable through the `mktime` function. 

Elements	Represent
`tm_sec`	Seconds passed in a minute
`tm_min`	Minutes passed in an hour
`tm_hour`	Hours passed in a day
`tm_mday`	Months passed in a year
`tm_mon`	Months passed in a year
`tm_wday`	Days passed in a week
`tm_yday`	Days passed in a year
`tm_year`	Years passed since 1900
`tm_isdst`	Daylight saving hours

What is mtkime in C?

Function syntax

Parameters

Return value

Example