time calculation

[cpliu]

I'd like to count the total hours by one column deducted by another.

Format:
When I entered the time, I didn't put AM and PM into consideration. So
cell is considered AM. How can I change the whole column from AM to PM
without affecting the numbers? For examples, it shows 9:10 and it's
9:10pm instead of changing to 21:10 in cell?

How to calculate the hours between 7:04am to the 1:03am of the next
day? The deduction turns to ######.

Thanks for the help,

 

[liu]

When I enter time code of video in a cell, it always think it's the
clock time. if I enter 34:44, it changes it to 10:44. How can I format
it so it's hh:mm:ss? I've tried entering mm:ss as custom format, but
it changed it 44:00. H:mm:ss requires entering extra 0: for hours.

Thanks for the help,

 

[RagDyer]

In an unused,empty cell enter
0.5

Right click in that cell and choose "Copy".
Select all the cells in that time column, and right click in that selection.
Choose <Paste Special> <Add> <OK>

NOW, while that column is *still* selected,
from the Menu Bar:
<Format> <Cells> <Number> tab,
Click on "Time",
And then select a time format from "Type" window that's to your liking,
Then <OK>,
And you're done!

Don't forget to clear the cell with the 0.5 in it.

 

[Gary''s Student]

If you entered 9:10 in A1 ( its actually 9:10 AM ), in B1 enter:

=A1+.5 and format as Time.

 

[RagDyer]

Forgot the second part of your question.

With start time in A18, and end time in B18, use this to calculate the
difference:

=MOD(B18-A18,1)

 

[Gary''s Student]

Its O.K. to format the cell as hh:ss, but you must still enter the value as
0:34:20 to get 34 minutes and 20 seconds.