How to Calculate Differences in Time

In the course of a day, you may have two separate events that can occur. If you want to know how much time elapsed between these two points in time, then you need to know how to calculate the difference in time. The difference in time is not as easy as simple subtraction because time uses a 60-minute base instead of a 100 base. It is often easier to subtract time using military time.

• 1

  Convert the times to military time. The Resources include a link to a conversion table. For example, 5:05 a.m. and 6:02 p.m. are 0505 and 1802.

• 2

  Subtract the hours. In the example in Step 1, 18 minus 5 equals 13 hours.

• 3

  Subtract the minutes. If the later time's minutes are greater than the earlier time's, then you only need to subtract the minutes. If the later time's minutes are less than the earlier time's, then first deduct an hour from your hour calculation. Second, subtract the earlier time's minutes from 60 and then add the later times minutes. In the example, deduct one hour from 13 hours to get 12 hours. Then, subtract five from 60, which is 55, and add two minutes. So, the difference between 5:05 a.m. and 6:02 p.m. is 12 hours and 57 minutes.