- Work out the addition or subtraction time using days, hours, minutes, and seconds easily
- The time duration calculator can add or subtract days,hours, minutes, and seconds between two values. This can be helpful as time is calculated in a variety of ways making calculations more difficult then simple numerical additions or subtractions. For instance, time is based on a number system that uses 60 as its base while days are measured in 24-hour periods.
- Using the time duration calculator
- The time duration calculator is very easy to use as long as you can provide two time variables to either add or subtract.
- 1. On the first line of the calculator include the initial units of days, hours, minutes, and seconds. If a variable is not applicable, please set the field to zero.
- 2. On the second line of the calculator using the drop down feature, select (+) to add units of time or (–) if you want to subtract time units.
- 3. Then proceed to the third line of the calculator where you may include the next variables of days, hours, minutes, and seconds, using zero when no value is present.
- 4. Once this is done, click on “Calculate” to find out the sum of your equation.
- The calculator does not have to be reset for new calculations, simply adjust the necessary fields and click “Calculate” when ready.
- Continue reading for a step-by-step guide on the mathematical principles of adding and subtracting time, as well as some practice questions to try out.
- Principles of adding time
- When adding time all values of days, minutes, seconds and hours should be calculated separately, then adjusted based on the numerical system being used.
- 1. First add the days
- 2. Then add the hours
- 3. Finish by adding the minutes and seconds
- 4. Adjust the hours, minutes, and seconds according to the numerical base
- • If the hours are more then 24, subtract 24 from the hours and add 1 to the days.
- • If the minutes are 60 or more, subtract 60 from THE minutes and add 1 to the hours.
- • If the seconds are more then 60, subtract 60 from the seconds and add 1 to the minutes.

- Principles of subtracting time
- When subtracting time, similar principles apply.
- 1. First subtract the days
- 2. Then subtract the hours
- 3. Finish by subtracting the minutes and seconds
- 4. Adjust the hours, minutes, and seconds according to the numerical base
- • If the hours are negative, add 24 to the hours and subtract 1 from the days.
- • If the minutes are negative, add 60 to the minutes and subtract 1 from the hours.
- • If the seconds are negative, add 60 to the seconds and subtract 1 from the minutes.

- Your turn to test yourself
- Try out these next time equations and check your work with the time duration calculator. Remember the steps listed above, and reference the examples if you get stuck.