How does UA handle time zones? For instance, as I type this it's not yet 2015 in Hawaii. Are they also seeing zeros now?
UA's systems seem to operate on Central time, which makes sense given that both Chicago and Houston are in Central. I think this is responsible for the somewhat-notorious Hawaii CPU bug where CPU sweeps for redeyes out of HI (and flights after 11pm Pacific) run 24 hours early.
Anyway, that suggests that the UA ball drops at 12 am Chicago time. Which is consistent with the reports in this thread.