Calculating the Difference Between Two Time Periods in C

In programming, it's often necessary to calculate the difference between two time periods, whether it's to find the difference between two dates or subtract one time value from another.

In C, you can achieve this using the time.h library, which provides the necessary tools to handle date and time manipulations.

 

Objective

In this article, we will calculate the difference between two time periods in C using the struct tm structure, which represents a time and date. We'll follow a structured approach with clear steps and code comments.

 

Prerequisites

• Basic understanding of C programming

• Familiarity with the time.h library

 

Code Example

// Calculating the Difference Between Two Time Periods in C
#include <stdio.h>
#include <time.h>

// The main function of the program
int main()
{
    // Step-1 Declare and initialize time variables
    struct tm time1 = {0};  // Initializing time1 to zero
    struct tm time2 = {0};  // Initializing time2 to zero

    // Step-2 Input the first time period (time1)
    time1.tm_year = 2025 - 1900;  // tm_year is year since 1900
    time1.tm_mon = 4;             // Month is 0-based (0 = January)
    time1.tm_mday = 1;            // Day of the month
    time1.tm_hour = 10;           // Hour (24-hour format)
    time1.tm_min = 30;            // Minutes
    time1.tm_sec = 0;             // Seconds

    // Step-3 Input the second time period (time2)
    time2.tm_year = 2025 - 1900;
    time2.tm_mon = 4;
    time2.tm_mday = 9;
    time2.tm_hour = 15;
    time2.tm_min = 45;
    time2.tm_sec = 0;

    // Step-4 Convert struct tm to time_t for both time periods
    time_t t1 = mktime(&time1);
    time_t t2 = mktime(&time2);

    // Step-5 Calculate the difference in seconds
    double difference = difftime(t2, t1);

    // Step-6 Convert the difference to hours, minutes, and seconds
    int hours = difference / 3600;  // 3600 seconds in an hour
    int minutes = (difference - (hours * 3600)) / 60;  // Remaining minutes
    int seconds = difference - (hours * 3600) - (minutes * 60);  // Remaining seconds

    // Step-7 Output the result
    printf("\nTime difference: %d hours, %d minutes, %d seconds\n", hours, minutes, seconds);

    return 0;
}

Run

Output

 

Explanation of the Code:

1. Declare Time Variables: We declare two struct tm variables (time1 and time2) to store the two time periods.

2. Input Time Periods: We manually input values for time1 and time2. The months are 0-based (i.e., 0 for January), so we subtract 1 when setting the month.

3. Convert to time_t: We use the mktime() function to convert the struct tm into a time_t value, which represents the time in seconds since the Unix epoch (January 1, 1970).

4. Calculate the Difference: The difftime() function calculates the difference in seconds between time2 and time1.

5. Convert to Human-Readable Format: We then calculate hours, minutes, and seconds from the difference in seconds.

6. Output the Result: Finally, we output the calculated time difference.

 

Output Example:

For the time periods 2025-05-01 10:30:00 and 2025-05-09 15:45:00, the output will be:

 

Examples in other languages

C++

// DIFFERENCE BETWEEN TWO TIME PERIODS in C++ using time.h
#include <iostream>
#include <ctime>
using namespace std;

int main()
{
    // Step-1 Declare two time structures
    struct tm time1 = {0}, time2 = {0};

    // Step-2 Assign values to both time structures
    time1.tm_year = 2025 - 1900;
    time1.tm_mon = 4;
    time1.tm_mday = 1;
    time1.tm_hour = 10;
    time1.tm_min = 30;
    time1.tm_sec = 0;

    time2.tm_year = 2025 - 1900;
    time2.tm_mon = 4;
    time2.tm_mday = 9;
    time2.tm_hour = 15;
    time2.tm_min = 45;
    time2.tm_sec = 0;

    // Step-3 Convert tm to time_t
    time_t t1 = mktime(&time1);
    time_t t2 = mktime(&time2);

    // Step-4 Calculate difference
    double diff = difftime(t2, t1);

    int hours = diff / 3600;
    int minutes = ((int)diff % 3600) / 60;
    int seconds = (int)diff % 60;

    // Step-5 Print result
    cout << "\nTIME DIFFERENCE: " << hours << " HOURS, " << minutes << " MINUTES, " << seconds << " SECONDS\n";

    return 0;
}

Run

 

Java

// DIFFERENCE BETWEEN TWO TIME PERIODS in Java using LocalDateTime
import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // Step-1 Create two LocalDateTime instances
        LocalDateTime time1 = LocalDateTime.of(2025, 5, 1, 10, 30, 0);
        LocalDateTime time2 = LocalDateTime.of(2025, 5, 9, 15, 45, 0);

        // Step-2 Calculate time difference
        long diffInSeconds = ChronoUnit.SECONDS.between(time1, time2);

        // Step-3 Convert to hours, minutes, seconds
        long hours = diffInSeconds / 3600;
        long minutes = (diffInSeconds % 3600) / 60;
        long seconds = diffInSeconds % 60;

        // Step-4 Print result
        System.out.println("\nTIME DIFFERENCE: " + hours + " HOURS, " + minutes + " MINUTES, " + seconds + " SECONDS");
    }
}

Run

 

C#

// DIFFERENCE BETWEEN TWO TIME PERIODS in C# using DateTime
using System;

public class W3CW
{
    public static void Main()
    {
        // Step-1 Define two DateTime variables
        DateTime time1 = new DateTime(2025, 5, 1, 10, 30, 0);
        DateTime time2 = new DateTime(2025, 5, 9, 15, 45, 0);

        // Step-2 Get difference as TimeSpan
        TimeSpan difference = time2 - time1;

        // Step-3 Print time difference
        Console.WriteLine("\nTIME DIFFERENCE: {0} HOURS, {1} MINUTES, {2} SECONDS",
            difference.Hours + difference.Days * 24, difference.Minutes, difference.Seconds);
    }
}

Run

 

Python

# DIFFERENCE BETWEEN TWO TIME PERIODS in Python using datetime
from datetime import datetime

# Step-1 Define two datetime values
time1 = datetime(2025, 5, 1, 10, 30, 0)
time2 = datetime(2025, 5, 9, 15, 45, 0)

# Step-2 Get difference
diff = time2 - time1
total_seconds = diff.total_seconds()

# Step-3 Convert to hours, minutes, seconds
hours = int(total_seconds // 3600)
minutes = int((total_seconds % 3600) // 60)
seconds = int(total_seconds % 60)

# Step-4 Print result
print(f"\nTIME DIFFERENCE: {hours} HOURS, {minutes} MINUTES, {seconds} SECONDS")

Run

 

JavaScript

// DIFFERENCE BETWEEN TWO TIME PERIODS in JavaScript using Date
const time1 = new Date(2025, 4, 1, 10, 30, 0); // Month is 0-indexed
const time2 = new Date(2025, 4, 9, 15, 45, 0);

// Step-1 Calculate difference in milliseconds
const diff = time2 - time1;

// Step-2 Convert to hours, minutes, seconds
const hours = Math.floor(diff / 3600000);
const minutes = Math.floor((diff % 3600000) / 60000);
const seconds = Math.floor((diff % 60000) / 1000);

// Step-3 Print result
console.log(`\nTIME DIFFERENCE: ${hours} HOURS, ${minutes} MINUTES, ${seconds} SECONDS`);

 

Go

// DIFFERENCE BETWEEN TWO TIME PERIODS in Go using time package
package main

import (
	"fmt"
	"time"
)

func main() {
	// Step-1 Create two time values
	time1 := time.Date(2025, 5, 1, 10, 30, 0, 0, time.UTC)
	time2 := time.Date(2025, 5, 9, 15, 45, 0, 0, time.UTC)

	// Step-2 Get difference in seconds
	diff := time2.Sub(time1).Seconds()

	// Step-3 Convert to hours, minutes, seconds
	hours := int(diff) / 3600
	minutes := (int(diff) % 3600) / 60
	seconds := int(diff) % 60

	// Step-4 Print result
	fmt.Printf("\nTIME DIFFERENCE: %d HOURS, %d MINUTES, %d SECONDS\n", hours, minutes, seconds)
}

 

Rust

// DIFFERENCE BETWEEN TWO TIME PERIODS in Rust using chrono
use chrono::{NaiveDateTime};

fn main() {
    // Step-1 Define two datetime values
    let time1 = NaiveDateTime::parse_from_str("2025-05-01 10:30:00", "%Y-%m-%d %H:%M:%S").unwrap();
    let time2 = NaiveDateTime::parse_from_str("2025-05-09 15:45:00", "%Y-%m-%d %H:%M:%S").unwrap();

    // Step-2 Calculate difference
    let diff = time2.signed_duration_since(time1).num_seconds();

    // Step-3 Convert to hours, minutes, seconds
    let hours = diff / 3600;
    let minutes = (diff % 3600) / 60;
    let seconds = diff % 60;

    // Step-4 Print result
    println!("\nTIME DIFFERENCE: {} HOURS, {} MINUTES, {} SECONDS", hours, minutes, seconds);
}

 

Swift

// DIFFERENCE BETWEEN TWO TIME PERIODS in Swift using Date
import Foundation

let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

let time1 = formatter.date(from: "2025-05-01 10:30:00")!
let time2 = formatter.date(from: "2025-05-09 15:45:00")!

let diff = time2.timeIntervalSince(time1)

let hours = Int(diff) / 3600
let minutes = (Int(diff) % 3600) / 60
let seconds = Int(diff) % 60

print("\nTIME DIFFERENCE: \(hours) HOURS, \(minutes) MINUTES, \(seconds) SECONDS")

 

Kotlin

// DIFFERENCE BETWEEN TWO TIME PERIODS in Kotlin using LocalDateTime
import java.time.LocalDateTime
import java.time.temporal.ChronoUnit

fun main() {
    // Step-1 Define two datetime values
    val time1 = LocalDateTime.of(2025, 5, 1, 10, 30, 0)
    val time2 = LocalDateTime.of(2025, 5, 9, 15, 45, 0)

    // Step-2 Calculate difference in seconds
    val diff = ChronoUnit.SECONDS.between(time1, time2)

    // Step-3 Convert to hours, minutes, seconds
    val hours = diff / 3600
    val minutes = (diff % 3600) / 60
    val seconds = diff % 60

    // Step-4 Print result
    println("\nTIME DIFFERENCE: $hours HOURS, $minutes MINUTES, $seconds SECONDS")
}

 

PHP

// DIFFERENCE BETWEEN TWO TIME PERIODS in PHP using strtotime
<?php

$time1 = strtotime("2025-05-01 10:30:00");
$time2 = strtotime("2025-05-09 15:45:00");

$diff = $time2 - $time1;

$hours = floor($diff / 3600);
$minutes = floor(($diff % 3600) / 60);
$seconds = $diff % 60;

echo "\nTIME DIFFERENCE: $hours HOURS, $minutes MINUTES, $seconds SECONDS\n";
?>

Run

 

Ruby

# DIFFERENCE BETWEEN TWO TIME PERIODS in Ruby using Time
require 'time'

time1 = Time.parse("2025-05-01 10:30:00")
time2 = Time.parse("2025-05-09 15:45:00")

diff = time2 - time1

hours = (diff / 3600).to_i
minutes = ((diff % 3600) / 60).to_i
seconds = (diff % 60).to_i

puts "\nTIME DIFFERENCE: #{hours} HOURS, #{minutes} MINUTES, #{seconds} SECONDS"

 

R

# DIFFERENCE BETWEEN TWO TIME PERIODS in R using difftime
time1 <- as.POSIXct("2025-05-01 10:30:00", tz = "UTC")
time2 <- as.POSIXct("2025-05-09 15:45:00", tz = "UTC")

diff <- as.numeric(difftime(time2, time1, units = "secs"))

hours <- diff %/% 3600
minutes <- (diff %% 3600) %/% 60
seconds <- diff %% 60

cat("\nTIME DIFFERENCE:", hours, "HOURS,", minutes, "MINUTES,", seconds, "SECONDS\n")

 

Scala

// DIFFERENCE BETWEEN TWO TIME PERIODS in Scala using LocalDateTime
import java.time.LocalDateTime
import java.time.temporal.ChronoUnit

object W3CW extends App {
    val time1 = LocalDateTime.of(2025, 5, 1, 10, 30, 0)
    val time2 = LocalDateTime.of(2025, 5, 9, 15, 45, 0)

    val diff = ChronoUnit.SECONDS.between(time1, time2)

    val hours = diff / 3600
    val minutes = (diff % 3600) / 60
    val seconds = diff % 60

    println(s"\nTIME DIFFERENCE: $hours HOURS, $minutes MINUTES, $seconds SECONDS")
}

 

Conclusion

Using the time.h library in C, calculating the difference between two time periods is simple and effective. By following the steps above, you can easily compute the difference in seconds, minutes, hours, or even days.

This technique is useful for various applications, including scheduling, event tracking, and date-time calculations.