Please note that for most of the large superspreading events in the US as well as in some other countries the index dates in the database are placeholders (in the database these cells are marked light red in the Index Date column).
The focus of the database is on the features of the settings in which superspreading events took place, and on the general period in which they occurred, specifically whether they occurred in flu season or not. Finding the exact dates for more than 900 superspreading events would require a disproportionate amount of time. What this does mean is that no conclusions about the spread of the virus in the US and those countries should be drawn from the timeline.
Also note that many superspreading events in the database occurred over an extended period of time rather than on one specific day. Mardi Gras festivities, for example, typically are a weeks-long event, and outbreaks in prisons, nursing homes and meat processing plants also take place over an extended period of time.