In cells adjacent to your "dates" enter this

=ISNUMBER(A1) where A1 is the address of a cell with a time.

I'm guessing you get some values with FALSE.

Here are some ideas on how to do a global convert.

http://www.contextures.com/xlDataEntry03.html

I've done it with Text to Columns, and I think there is an option to change
the column from GENERAL to a date. You may want to do that and then reformat
to HH:MM (or whatever you need).

--
HTH,
Barb Reinhardt



"orquidea" wrote:

Hi David:

I did what you suggested but it didn't work. The weird thing is that if I
run the formula from A1 to A50 It works but after that it doesn't. I
confirmed that the format is hh:mm in all of the data in that columm. I have
copied to a new sheet clear of any format and it doesn't work either.

Any idea what the problem is?

Thanks in advance

Orquidea



"David Biddulph" wrote:

You've presumably got text, rather than real times, in those cells?

Try putting 0:00 in a spare cell, select & copy, then select your column of
"times" and Edit/ Paste Special/ Add.
--
David Biddulph

"orquidea" wrote in message
...
Hi

I have a colum of 514 rows with hours information (15:00, 0:30, etc). I
want to get the maximun number of hours within this range. I have used
the
formula =max(a1:a514) but the outcome is 0:00. I have done this
calculation
before with hours and it has worked. The ranges have been smaller,
though.

Could anyone help me to figure out how to do it or why it is not working?

Thanks,
Orquidea