"These support races will run alongside the championship, usually being on the same date as the championship race on the given track"
Hypothetical example. Our first ILMC championship race on Silverstone could be hosted on march 8th at 19.00GMT. And then the Silverstone support race would be hosted on the same date at 13.00GMT. So yeah, these events will either be on the same date as the championship race on the given track, or a day before.
You were added to the list the very moment you were writing your last comment, Harsk100.