After Vincas showed me how to dump a mysql database (Saturday-ish) and prodded me to write a script to edit the dates (Saturday and Sunday), I have now done so, deleted my tables (having googled the command), and set things back up with that edited dump file. Wow.
I used php to do it though, not the perl Vincas suggested. And I am quite sure there is a cleaner way to do it than the script I used, but it was functional. So now my posts are more or less in the right day (give or take gmt messiness), and displaying with the right time (IF you pretend daylights savings time never existed). Yay!