## Calculator: Time Duration - Add Subtract Time

#### How to Calculate Time Duration?

**Step 1: Identify Start Time and End Time**

For e.g.:

Start Time: 9:45 a.m

End Time: 1:25 p.m.

**Step 2: Convert to 24-hour clock**

It times are given in 12-hour clock, then convert it to 24-hour clock notation.

12-hour clock time in AM is the same as 24-hour clock time. For 12-hour clock time in p.m., we add 12 hours to change it to 24-hour clock time. Only exception is if it is 12pm then it stays 12 in 24-hour clock as well.

Start Time (in 24-hour clock): 09 45 hrs

End Time (in 24-hour clock): 1+12 = 13 = 13 25 hrs

**Step 3: Subtract Minutes**

If minutes in the end time is greater than minutes in the start time, then subtract normally to get the minutes duration. If minutes in end time is less than minutes in the start time then add 60 to the end time minutes and reduce the hour by 1. Then proceed to subtract minutes from the start time.

In our example:

End Time Minutes = 25

Start Time Minutes = 45

Since end time minutes is less than start time minutes, we make end time minutes = 25 + 60 = 85 (remember to reduce 1 from hour time i.e. make it 13 - 1 = 12).

Minutes Duration = 85 - 45 = 40

**Step 4: Subtract Hours**

End Time Hours = 12 (Since we already borrowed 60 minutes from it hence it reduced by 1)

Start Time Hours = 09

Hours Duration = 12 - 9 = 3

Hence, the duration between 9:45 a.m. and 1:25 p.m. is 3 hours and 40 minutes.