Comment 10 for bug 105519

casper isn't touching the clock at boot time.
ntpdate is triggered by ifupdown which sets the clock to the right time. The timezone is going to be UTC until a location is selected in ubiquity at which point the clock will change to reflect the timezone change.

I think the current behaviour is correct, though it indeed could be slightly improved by having NetworkManager parse the dhcp flag and expose that to the desktop environment somehow.