I don't think that the pack changed working hours. Ive heard that some of the careers in Bridgeport have their hours slightly altered to fit better with the night life theme, but I'm not sure if that's true.
Most careers have their days set as Mon-Fri because that's how a lot of jobs in the real world work too.
Blind probably, lol, kidding, but in LN pretty much every job is set back till around lunch time, to start work, and you get off like 10ish or so. That way your sim can party all night, have a hangover and still go to work.
When I first started playing, I thought there was something wrong with my game for the same reason, lol. When I got a little up the job ladder, the days started changing up a little. A lot of jobs just happen to be like that ;P