Valid RSS / XML date

Do not use [code:1:de0723684d]date(DATE_RFC822);[/code:1:de0723684d]

use:
[code:1:de0723684d]date(DATE_RSS);[/code:1:de0723684d] instead. This gives a pass at the W3 feed validator as it has a full year (2010) instead of (10)

You can use this for at least:
pubDate
lastBuildDate