08:00 GMT tomorrow
But I can give you a preview:
It will become abundantly clear Harris will very likely win more than 270 Electoral College votes (the threshold to win the election, even with some states still receiving and counting votes well after today) around 23:00 GMT, but by then Trump and his cronies will have already begun declaring the election rigged, claiming—without credible evidence—that there was widespread fraud orchestrated by the “cheating Democrats”, and will refuse to concede.
That will begin the weeks long process of Republican governors and state/local officials of several swing states either attempting to resist intense pressure from the MAGA camp to help Trump or executing a preplanned operation to help Trump, with hundreds of lawsuits filed from both sides regarding election practices and counts (on top of the ones already filed prior to the election, mostly by Republicans to setup the “rigged election” narrative).