It is a bit confusing. My guess is that they want to halt trading on the 9th and they have to decide at what time they want to do that. They chose 8:30 CT.
The day before Bush’s national day of mourning saw the averages down about 3%. I recall trading that day. Huge whipsaws daily with China trade talks. With volatility already up be prepared for fun times in January. MLK day in 2008 was a fun one as well, traded through that liquidation when futures markets were open and world markets were falling 5%+ It seems like things are lining up similar to February 2018 when we had the volitility explosion on the 5th, traded that one too. Should have some great trading coming up this year.