Some dates recognized as dates, some dates not recognized. Why?

Here is a list of dates:

04-22-11

12-19-11

11-04-11

12-08-11

09-27-11

09-27-11

04-01-11

When you copy this list in Excel, some of them are recognized as dates, others not, in the following manner:

04-22-11

12-19-11

11-04-11 (date)

12-08-11 (date)

09-27-11

09-27-11

04-开发者_如何学Go01-11 (date)

Does anyone know why? And how to force Excel to recognize all list items as dates?

Many thanks!

It is caused by Excel auto-recognizing/formatting the cell contents, but in unclear/inconsistent ways. Fixing it is not that hard...

Check out this forum post:

http://www.pcreview.co.uk/forums/excel-not-recognizing-dates-dates-t3139469.html

The steps in short:

1. Select only the column of "dates"
2. Click Data > Text to Columns
3. Click Next
4. Click Next
5. In step 3 of the wizard, check "Date" under Col data format, then choose: "DMY" from the droplist.
6. Click Finish

This is caused by the regional settings of your computer.

When you paste data into excel it is only a bunch of strings (not dates).

Excel has some logic in it to recognize your current data formats as well as a few similar date formats or obvious date formats where it can assume it is a date. When it is able to match your pasted in data to a valid date then it will format it as a date in the cell it is in.

Your specific example is due to your list of dates is formatted as "m/d/yy" which is US format. it pastes correctly in my excel because I have my regional setting set to "US English" (even though I'm Canadian :) )

If you system is set to Canadian English/French format then it will expect "d/m/yy" format and not recognize any date where the month is > 13.

The best way to import data, that contains dates, into excel is to copy it in this format.

2011-04-22
2011-12-19
2011-11-04
2011-12-08
2011-09-27
2011-09-27
2011-04-01

Which is "yyyy-MM-dd", this format is recognized the same way on every computer I have ever seen (is often refered to as ODBC format or Standard format) where the units are always from greatest to least weight ("yyyy-MM-dd HH:mm:ss.fff") another side effect is it will sort correctly as a string.

To avoid swaping your regional settings back and forth you may consider writting a macro in excel to paste the data in. a simple popup format and some basic logic to reformat the dates would not be too difficult.

In your case it is probably taking them in DD-MM-YY format, not MM-DD-YY.

The quickest and easiest way to fix this is to do a find and replace on your date seperator, with the same separator. For example in this case Find "-" and Replace with "-", not sure why this works but you will find all dates are right-aligned as they should be after doing this.

Here is what worked for me. I highlighted the column with all my dates. Under the Data tab, I selected 'text to columns' and selected the 'Delimited' box, I hit next and finish. Although it didn't seem like anything changed, Excel now read the column as dates and I was able to sort by dates.

The simplest solution is to put yy,mm,dd into the date() formula by first extracting them with left(), mid() and right(). In this case, assuming your input date is in A1:

=date(right(A1,2)+100,left(A1,2),mid(A1,4,2))

Explanation of above:

=right(A1,2) gets the last two digits in the cell (yy). We add 100 because it defaults to 1911 instead 2011 (omit +100 if it doesn't do that on yours)

=left(A1,2) gets the first two digits in the cell (mm).

=mid(A1,4,2) gets 2 digits in the middle of the cell, starting at 4th digit (dd).

Why this happens in the first place:

I come across this problem all the time when I import Canadian bank data into excel. In short, your input date format does not match your regional settings.

Seems your setting mean Excel wants date input as either DD-MM-YY or YY-MM-DD, but your input data is formatted as MM-DD-YY.

So, excel sees your days as months and vice-versa, which means any date with day below 12 will be recognized as a date, BUT THE WRONG DATE (month and day reversed) and any date with day above 12 won't be recognized as a date at all, because Excel sees the day as a 13th+ month.

Unfortunately, you can't just change the formatting, because Excel has already locked those day/month assignments in place, and you just end up moving what Excel THINKS are days and months around visually, not reassigning them.

Frankly, it is surprising to me there is not a date-reverse tool in excel, because I would think this happens all the time. But the formula above does it pretty simply.

NOTE: if your dates don't have leading zeros (i.e. 4/8/11 vs 04/08/12) it gets trickier because you have to extract different amounts of digits depending on the date (i.e. 4/9/11 vs 4/10/11). You then have to build a couple if statements in your formula. Gross.

Here is what worked for me on a mm/dd/yyyy format:

=DATE(VALUE(RIGHT(A1,4)),VALUE(LEFT(A1,2)),VALUE(MID(A1,4,2)))

Convert the cell with the formula to date format and drag the formula down.

Right-click on the column header and select Format Cells, the chose Date and select the desired date format. Those that are not recognized are ambiguous, and as such not interpreted as anything but that is resolved after applying formatting to the column. Note that for me, in Excel 2002 SP3, the dates given above are automatically and correctly interpreted as dates when pasting.

A workaround for this problem consists in temporarily changing your regional settings, so the date format of the CSV imported file "matches" the regional settings one.

Open Office seems to work in a similar way for that issue, see: http://www.oooforum.org/forum/viewtopic.phtml?t=85898

I come across this problem when I tried to convert to Australian date format in excel. I split the cell with delimiter and used the following code from split cells then altered the issue areas.

=date(dd,mm,yy)