I have a lot of historical content I'm about to add to my blog. It's about pro wrestling and I'm going to add match results that were on a weekly basis since 1996! Now if I use the wordpress feature where you can submit a new post in the past via the date. (Hope I'm making that clear). Like you can just type in July 22nd 2002 and it appears in the blogs archives. My questions is will these show up in the sitemap and get crawled, considering they are perceived to be old, even though I really just posted them.
As long as you have a sitemap plugin it will still work. Worst case scenario you will need to click rebuild your sitemap. Nothing major.