How do I fix PHP Notice - Undefined index: releaseDate? I'm getting this error: 

Undefined index: releaseDate in craft/app/etc/behaviors/AppBehavior.php(500)

Line 500: $row['releaseDate'] = DateTime::createFromString($row['releaseDate'], null, false);


Is there anything I can do to fix this?
I've run into this issue myself with Craft version: 2.6.2962.

The line in question is expecting a column from the database called "releaseDate".
In my case, that column no longer exists. It might have gotten dropped or lost with one of the updates, I am not sure.

A short-term solution would be to edit that line of code and pass in some different value.

In my case, I changed the line to:

$row['releaseDate'] = DateTime::createFromString($row['dateUpdated'], null, false);


And to clarify, looking at the changelog, it seems they are in the process of tweaking the craft()->releaseDate() function call.

Update 03/06/2017:
It appears that my code-base was outdated with the version in my database. I updated to the latest version of craft and that line that I edited above is now gone.

My question to you: Is your craft version up to date?