Time Duration Calculator

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time duration calculator
Difference Between Two Dates/TimesAdd Time to a DateSubtract Time from a Date
Result:
function toggleInputs(){var mode=document.getElementById('calc_mode').value;var endRDate=document.getElementById('endRowDate');var endRTime=document.getElementById('endRowTime');var durRow=document.getElementById('durationRow');if(mode==='diff'){endRDate.style.display='table-row';endRTime.style.display='table-row';durRow.style.display='none';}else{endRDate.style.display='none';endRTime.style.display='none';durRow.style.display='table-row';}}function calculateDuration(){var mode=document.getElementById('calc_mode').value;var sDateVal=document.getElementById('start_date').value;var sTimeVal=document.getElementById('start_time').value;if(!sDateVal){alert('Please select a start date');return;}var start=new Date(sDateVal+'T'+sTimeVal);var resultText="";var totalMs=0;if(mode==='diff'){var eDateVal=document.getElementById('end_date').value;var eTimeVal=document.getElementById('end_time').value;if(!eDateVal){alert('Please select an end date');return;}var end=new Date(eDateVal+'T'+eTimeVal);totalMs=end-start;if(isNaN(totalMs)){alert('Invalid Date Input');return;}var diff=Math.abs(totalMs);var days=Math.floor(diff/(1000*60*60*24));var hours=Math.floor((diff%(1000*60*60*24))/(1000*60*60));var mins=Math.floor((diff%(1000*60*60))/(1000*60));resultText=days+" days, "+hours+" hours, and "+mins+" minutes";}else{var dD=parseInt(document.getElementById('d_days').value)||0;var dH=parseInt(document.getElementById('d_hours').value)||0;var dM=parseInt(document.getElementById('d_mins').value)||0;var offset=(dD*24*60*60*1000)+(dH*60*60*1000)+(dM*60*1000);var resDate=new Date(start.getTime()+(mode==='add'?offset:-offset));resultText=resDate.toLocaleString();totalMs=offset;}document.getElementById('resultValue').innerHTML=resultText;if(document.getElementById('show_breakdown').checked && mode==='diff'){var tHrs=Math.floor(Math.abs(totalMs)/(1000*60*60));var tMins=Math.floor(Math.abs(totalMs)/(1000*60));document.getElementById('breakdown').innerHTML="Total Hours: "+tHrs.toLocaleString()+"
Total Minutes: "+tMins.toLocaleString();}else{document.getElementById('breakdown').innerHTML="";}document.getElementById('answer').style.display='block';}

Calculator Use

The time duration calculator is a versatile tool designed to measure the exact length of time between two points or to adjust a specific date and time by a certain amount. Whether you are calculating hours worked for a payroll sheet, determining the age of an event, or planning a project timeline, this tool provides precise results instantly.

This calculator supports three primary modes: finding the difference between two dates and times, adding a specific duration to a date, or subtracting time from a starting point. It accounts for varying month lengths and can break down the results into days, hours, and minutes.

Start Date & Time
The beginning point of your calculation. For work hours, this would be your "clock-in" time.
End Date & Time
The finishing point. Used when calculating the span or elapsed time between two events.
Duration (Days, Hours, Minutes)
The specific amount of time you wish to add to or subtract from your starting date.

How It Works

To use the time duration calculator effectively, you should understand how time spans are mathematically processed. The calculator converts all inputs into a standardized millisecond format based on the Unix epoch (January 1, 1970) to perform calculations before converting back into human-readable units.

Total Duration = (End Timestamp – Start Timestamp)

Once the total milliseconds are found, the following constants are applied to break down the result:

  • 1 Day = 86,400,000 milliseconds
  • 1 Hour = 3,600,000 milliseconds
  • 1 Minute = 60,000 milliseconds

Calculation Example

Example: Suppose you started a technical task on October 10th at 8:30 AM and finished it on October 12th at 5:45 PM. You need to find the total elapsed time.

Step-by-step solution:

  1. Start: Oct 10, 08:30
  2. End: Oct 12, 17:45 (24-hour clock)
  3. Calculate days: Oct 10 to Oct 12 = 2 Full Days (48 hours)
  4. Calculate time difference: 08:30 to 17:45 = 9 hours and 15 minutes
  5. Combine: 2 days, 9 hours, and 15 minutes
  6. Total in Hours: (2 * 24) + 9 = 57 hours and 15 minutes

Common Questions

How many hours are in a specific duration?

To find the total hours, multiply the number of days by 24 and add the remaining hours. For example, 3 days and 5 hours equals (3 * 24) + 5 = 77 hours. Our time duration calculator provides this breakdown automatically when the checkbox is selected.

Does this calculator account for Leap Years?

Yes, because the calculator uses standard Javascript Date objects, it inherently recognizes leap years (February 29th) and the correct number of days in each month when calculating spans across years.

What is the difference between "Time" and "Duration"?

Time refers to a specific point in the day (e.g., 2:00 PM), whereas duration refers to the length of an interval (e.g., 2 hours). This tool allows you to input both to find whichever missing variable you need.

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