the 220 Chart seems straight-forward; but the 827 Chart is more challenging. both involve space shuttle landing dates. 220 appears 19 days after the Columbia landing date; 827 appears 19 days after the Discovery landing date. Discovery actually had three launch dates: {1} 07-Aug-2005, the original landing date; {2} 08-Aug-2005, the extended landing date; & {3} 09-Aug-2005, the actual landing date. Discovery was scheduled to land in Florida (primary landing site), but due to bad weather landed in California (secondary landing site). the second landing date, 08-August, is 19 days from 27-August.
Hurricane Katrina (@ wikipedia) upgraded to category three hurricane on 27-August; President Bush declared a state of emergency in Louisiana, Alabama, and Mississippi. (btw, Governor of Louisiana, Kathleen Blanco declared a state of emergency on 26-August).
01-Feb-2003 - STS-107 Columbia disaster :: 20-Feb-2003 - Station nightclub fire
08-Aug-2005 - NASA Delays Discovery Landing :: 27-Aug-2005 - Hurricane Katrina