Time Calculation in Excel

Excel can work with time very easily.
Time can be entered in various different formats and calculations performed.
There are one or two oddities, but nothing which should put you off working with it.
See the TimeSheet example for an example.
Typing time
When time is entered into worksheet it should be entered with a colon between
the hour and the minutes, such as 12:30, rather than 12.30
	1:30	12:30	20:15	22:45
Excel can cope with either the 24hour system or the am/pm system.
To use the am/pm system you must enter the am or pm after the time.
You must leave a space between the number and the text.
	1:30 AM	1:30 PM	10:15 AM	10:15 PM
Finding the difference between two times
You can subtract two time values to find the length of time between.
	Start	End	Duration
	1:30	2:30	1:00	=D24-C24
	8:00	17:00	9:00	=D25-C25
	8:00 AM	5:00 PM	9:00 AM	If the result is not shown correctly,
				You may need to reformat the answer.
				Look at the section about formatting
				further in this worksheet.
Adding time
You can add time to find a total time.
This works well until the total time goes above 24 hours.
For totals greater than 24 hours you may need to apply some special formatting.
	Start	End	Duration
	1:30	2:30	1:00
	8:00	17:00	9:00
	7:30 AM	5:45 PM	10:15
			20:15
Formatting time
When time is added together the result may go beyond 24 hours.
Usually this gives an incorrect result, as in the example below.
To correct this error, the result needs to be formatted with a Custom format.
Example 1 : Incorrect formatting
	Start	End	Duration
	7:00	18:30	11:30
	8:00	17:00	9:00
	7:30	17:45	10:15
		Total	6:45	=SUM(E49:E51)
Example 2 : Correct formatting
	Start	End	Duration
	7:00	18:30	11:30
	8:00	17:00	9:00
	7:30	17:45	10:15
		Total	30:45	=SUM(E56:E58)
How To Apply Custom Formatting
The custom format for time use a pair of square brackets [hh] on either side
of the hours indicators.

1. Click on the cell which needs the format.

2. Choose the Format menu.

3. Choose Cells.

4. Click the Number tag at the top right.

5. Choose Custom.

6. Click inside the Type: box.

7. Type [hh]:mm as the format.

8. Click OK to confirm.

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