MovableType bug or feature?

This entry is posted at 8:20 local (12:20 GMT), but the the index.rdf entry will show the date as

<dc:date>2004-09-29T08:20:00-05:00</dc:date>

That seems to imply that the GMT offset is 5 hours, when (thanks to daylight savings time) it’s really 4 hours. So should MovableType put the current offset in there, or should anybody attempting to parse that file have to know about DST?