I think that may be it, although how that can happen is a mystery to me.
I copied it from the series of dates for 1999, only changing 1999 to
2000 using edit|replace. How could a date become a piece of text
pretending to be a date? And what's more important, how do I get it back
to being a date? When I format the cell to be a date, nothing really
happens.

Margo.

ScottO wrote:
Margo, is there any chance that the "date" in cell analysis2000!A2 is
actually a piece of text *pretending* to be a date?
Rgds,
ScottO

"Margo Guda" wrote in message
...
| I put this function:
|
(INDEX('2000'!$A$9:$I$8768,(DAY(analysis2000!$A2)-1)*24+1+analysis200
0!B$1,3))*0.447
| in a worksheet called analysis2000.
| This looks up a value in another worksheet (called 2000) based on
the
| date, which is stored in analysis2000!A2. I copied this out from
one
| working on a worksheet called 1999. It worked fine there. But for
this
| one, Excel 2000 returns the VALUE error on every instance. What I
am
| trying to do is putting a long list of hourly data (for a whole
year)
| into a matrix, one row for each day of the year. So 2000 has about
9000
| rows, analysis2000 has 366.
| The problem is in the DAY part of the function, which returns this
| error. Can anyone shed some light for me?
| Thanks in advance.
| Margo Guda.