The Time Calculator is a versatile tool designed to help you perform various operations with time durations. Whether you need to add or subtract specific amounts of time from a starting point, or determine the exact duration between two given times, this calculator simplifies complex time arithmetic. It's ideal for scheduling, project management, event planning, travel itinerary creation, or simply understanding time differences.
Add/Subtract Time
Use this section to find a future or past time by adding or subtracting hours, minutes, and seconds from a starting time.
Calculate Duration Between Two Times
Use this section to find the total time difference (duration) between a start time and an end time.
How the Time Calculator Works
This calculator performs two primary functions:
Adding/Subtracting Time: You input a starting time (e.g., 09:00:00) and then specify the number of hours, minutes, and seconds you wish to add or subtract. The calculator processes these values, correctly handling rollovers for minutes, hours, and days, to provide the resulting end time. For instance, adding 2 hours and 30 minutes to 09:00:00 will result in 11:30:00. Subtracting 1 hour from 01:00:00 will result in 00:00:00 (or 23:00:00 of the previous day if considering a 24-hour cycle).
Calculating Duration Between Two Times: Here, you provide two specific times (e.g., 10:00:00 and 14:45:30). The calculator then determines the absolute difference between these two points in time, presenting the result as a total duration in hours, minutes, and seconds. This is useful for measuring the length of an event, a work shift, or the travel time between two points.
Practical Examples
Scheduling a Meeting: If a meeting starts at 10:00:00 and is scheduled for 1 hour and 45 minutes, you can input 10:00:00 as the start time, 1 hour, and 45 minutes to find the end time: 11:45:00.
Project Deadline Adjustment: A task is due at 17:00:00, but you need to push it back by 3 hours and 15 minutes. Input 17:00:00, then add 3 hours and 15 minutes to get the new deadline: 20:15:00.
Travel Time Calculation: You leave home at 07:30:00 and arrive at your destination at 11:15:00. Using the duration calculator, you can find that your travel time was 3 hours, 45 minutes, and 0 seconds.
Shift Length: A worker clocks in at 08:00:00 and clocks out at 16:30:00. The duration calculator will show their shift length as 8 hours and 30 minutes.
.time-calculator-container {
font-family: Arial, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ccc;
border-radius: 8px;
background-color: #f9f9f9;
}
.time-calculator-container h2, .time-calculator-container h3 {
color: #333;
text-align: center;
margin-bottom: 15px;
}
.time-calculator-container p {
line-height: 1.6;
margin-bottom: 15px;
}
.calculator-section {
background-color: #eef;
padding: 15px;
border-radius: 5px;
margin-bottom: 20px;
border: 1px solid #ddd;
}
.calculator-section label {
display: inline-block;
width: 200px;
margin-bottom: 8px;
font-weight: bold;
}
.calculator-section input[type="text"],
.calculator-section input[type="number"] {
width: calc(100% – 210px);
padding: 8px;
margin-bottom: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.calculator-section button {
background-color: #007bff;
color: white;
padding: 10px 15px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
display: block;
width: 100%;
margin-top: 10px;
}
.calculator-section button:hover {
background-color: #0056b3;
}
.time-calculator-container div[id$="Result"] {
margin-top: 10px;
padding: 10px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
color: #333;
}
.time-calculator-container ul {
list-style-type: disc;
margin-left: 20px;
margin-bottom: 15px;
}
.time-calculator-container li {
margin-bottom: 8px;
}
// Helper function to parse HH:MM:SS string to total seconds since midnight
function parseTimeToSeconds(timeString) {
var parts = timeString.split(':');
if (parts.length !== 3) return NaN;
var h = parseInt(parts[0], 10);
var m = parseInt(parts[1], 10);
var s = parseInt(parts[2], 10);
if (isNaN(h) || isNaN(m) || isNaN(s) || h 23 || m 59 || s 59) {
return NaN;
}
return h * 3600 + m * 60 + s;
}
// Helper function to format total seconds into HH:MM:SS string
function formatSecondsToTime(totalSeconds) {
var sign = totalSeconds < 0 ? "-" : "";
totalSeconds = Math.abs(totalSeconds);
var h = Math.floor(totalSeconds / 3600);
var m = Math.floor((totalSeconds % 3600) / 60);
var s = totalSeconds % 60;
return sign +
(h < 10 ? '0' : '') + h + ':' +
(m < 10 ? '0' : '') + m + ':' +
(s < 10 ? '0' : '') + s;
}
// Helper function to format total seconds into HH:MM:SS duration string (can exceed 24 hours)
function formatSecondsToDuration(totalSeconds) {
var sign = totalSeconds 23
var m = Math.floor((totalSeconds % 3600) / 60);
var s = totalSeconds % 60;
return sign +
(h < 10 ? '0' : '') + h + 'h ' +
(m < 10 ? '0' : '') + m + 'm ' +
(s < 10 ? '0' : '') + s + 's';
}
function calculateEndTime() {
var startTimeStr = document.getElementById('startTimeInput').value;
var hoursDuration = parseInt(document.getElementById('hoursDurationInput').value, 10);
var minutesDuration = parseInt(document.getElementById('minutesDurationInput').value, 10);
var secondsDuration = parseInt(document.getElementById('secondsDurationInput').value, 10);
var resultDiv = document.getElementById('endTimeResult');
var startSeconds = parseTimeToSeconds(startTimeStr);
if (isNaN(startSeconds)) {
resultDiv.innerHTML = "Error: Invalid Start Time format. Please use HH:MM:SS.";
return;
}
if (isNaN(hoursDuration)) hoursDuration = 0;
if (isNaN(minutesDuration)) minutesDuration = 0;
if (isNaN(secondsDuration)) secondsDuration = 0;
var durationInSeconds = hoursDuration * 3600 + minutesDuration * 60 + secondsDuration;
var endSeconds = startSeconds + durationInSeconds;
// Handle time wrapping around 24 hours (0-86399 seconds)
var totalDaySeconds = 24 * 3600;
endSeconds = endSeconds % totalDaySeconds;
if (endSeconds < 0) {
endSeconds += totalDaySeconds; // Ensure positive result for negative wrap-around
}
resultDiv.innerHTML = "End Time: " + formatSecondsToTime(endSeconds);
}
function calculateDuration() {
var durationStartTimeStr = document.getElementById('durationStartTimeInput').value;
var durationEndTimeStr = document.getElementById('durationEndTimeInput').value;
var resultDiv = document.getElementById('durationResult');
var startSeconds = parseTimeToSeconds(durationStartTimeStr);
var endSeconds = parseTimeToSeconds(durationEndTimeStr);
if (isNaN(startSeconds) || isNaN(endSeconds)) {
resultDiv.innerHTML = "Error: Invalid Start or End Time format. Please use HH:MM:SS.";
return;
}
var diffSeconds = Math.abs(endSeconds – startSeconds);
resultDiv.innerHTML = "Duration: " + formatSecondsToDuration(diffSeconds);
}