Hey Jörg,
Yep it is a bug. It will be fixed in the next version. If you cannot wait, then go to components/com_hotspots/utils.php
Around line 394 you will find this code:
$rss_item->date = JHTML::Date($row->postdate);
change it to:
$rss_item->date = JFactory::getDate($row->postdate)->toRFC822();
The rss file had the correct date, but because the date hast to comply with the RFC822 standard:
asg.web.cmu.edu/rfc/rfc822.html
the rss readers were showing the date as 1970...
Cheers,
Daniel
P.S. Don't forget to delete the rss cache in media/com_hotspots/rss after you make the change.
P.S.1 And if you haven't already done so - please write a review in the jed