I get wrong date & time in article view, but correct date & time in category view
Example Category: Wednesday, 23 September 2009 12:51
Example Item (Article): Last modified on Tuesday, 30 November 1999 00:00

Hi. You are outputting the item's modification date on the item view. Probably this date is null so you get this error date. Try to output the item created date instead. We have made a simple check on the next release to avoid this. Thanks for reporting this issue.