将日期字符串从xml feed解析为DateTime

I have a few different xml feeds that I am consolidating into one "feed" for a website I'm working on (c#). Most of the feeds follow the rss2.0 standard, namely the news feeds and the facebook feed. However, I'm also pulling twitter and they seem to use their own standard from what I can tell. I am having an issue pulling the publish date from facebook and twitter because they are in slightly different formats.I have a few different xml feeds that I am cons