How to solve Warning: Missing required field "updated"

How to solve Warning: Missing required field "updated"

I think every Blogger have this problem on their snippets

Go to Template -Edit HTML- Check Expand Widgets

Press CTRL+F

Find this code

<a class='timestamp-link' expr:href='data:post.url' rel='bookmark' title='permanent link'><abbr class='published' expr:title='data:post.timestampISO8601'><data:post.timestamp/></abbr></a>

Change with this one

<a class='updated' expr:href='data:post.url' rel='bookmark' title='permanent link'><abbr class='updated' expr:title='data:post.timestampISO8601'><data:post.timestamp/></abbr></a>

Now Check it t again http://www.google.com/webmasters/tools/richsnippets?