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I tried to enter this date in ISO 8601 format (YYYY-MM-DD) in Excel 2010: 2012-04-08, but Excel automatically converts the date format to 4/8/2012.

I tried scrolling through the different types of Date formats that Excel allows me to choose from, but the 'YYYY-MM-DD' format isn't there:

Is there a way for Excel to recognize the ISO 8601 date format as a date value (and not automatically convert it to another format) when entered in a cell?

What you want is to use a custom format. Just type it in the box.

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Excel recognized your entry of yyyy-mm-dd, which is why it automatically converted it to your Regional Short Date format (Windows 7: Start > Control Panel > Region and Language > Formats).

What you wanted was for Excel to recognize and display the format.

In addition to the above, if you want a date that responds to the user's short date format, add an asterisk *yyyy-mm-dd. I don't recommend it, but you can do it.

I once did a list where we wanted items sorted by date, but for posting on the Web, we wanted to display only the year and month. We had our Date column where we entered the date in full yyyy-mm-dd. In a second column (B), we converted the date (=A2) to show only the year and month with the cell format: yyyy-mm. When it came time to post, we sort by Date, copy the other needed columns, say B-D, and paste on the Web page. WOrked like a charm.

I had been using the custom formats before. I changed my system region (Control Panel > All Control Panel Items > Region) to English (United Kingdom), short date to "yyyy-MM-dd" and Excel then did not auto correct from "2015-10-06" to "10/6/2015". It did not auto correct the other way though, but if you enter it that way it will stay that way. Saved me some time for sure!

This is what worked for me instead:
If it's a column of cells...

Select the column
Data tab then text to columns (in xl2003 menus)
choose fixed width, but don't have any delimiter lines
Choose Date (ymd)
This will convert the data to dates.

Now you can format the range the way you like.
credit goes to Dave here: http://msgroups.net/microsoft.public.excel.worksheet.functions/how-do-i-convert-d/75235

Custom formats are the obvious solution.

If you don't want to let go of the mouse, you can scroll the locale up one option from "English (United States)" to "English (United Kingdom)" and the YYYY-MM-DD format will appear among the choices.

There's a MUCH easier, safer way to do this:

In dates, just change your locale to Australia and poof! ANSI standard dates are available AND if you're in the US, Canada, Australia, or New Zealand, it doesn't monkey with your currency format, as all those countries all use the $ symbol.

Why--in their infinite wisdom--Microsoft doesn't make this available to ALL locales is a mystery, but it has been this way for years.