bill - 8:53 am on Apr 12, 2010 (gmt 0)
Welcome to WebmasterWorld dnab.
I'm afraid your feed will not validate if you don't give it the proper format for pubDate. All date-times in RSS conform to the Date and Time Specification of RFC 822 [asg.web.cmu.edu].
I wouldn't be concerned what shows up in various aggregators or viewers if the feed conformed to the standard and was valid. You can't control how others interpret the standard, but you can generally be safe by following it yourself.