>"That hasn't really been the case for quite some time. A majority of option and equity trading now happens directly rather than on open exchanges and is thus immune to "market hours"

Its not just the actual exchanges like the NYSE or NASDAQ but all of the other participants - the investment banks, the hedge funds, the ratings agencies, the analysts, the financial press. Following the sun, the day breaks first on the East Coast in the U.S. So yes while it could move to Boston, Mass, Charlotte, N.C. or back to Philadelphia where incidentally it was before Wall Street its probably limited to the boundaries of the Eastern Time Zone in U.S.