Some of those traders are used to how trading in futures, FX and other markets work, where they offer trading outside U.S. working hours, sometimes 24 hours ... midnight U.S. time might not ...

The NYSE and Cboe have both made similar announcements in recent months, as US exchanges look to enable greater global trading.

The next 12 hours, from midday to midnight, are called pm. However, you can tell the time without saying am and pm. To do this you can use the 24-hour clock. The 24-hour clock always uses 4 digits.