Stangman

I've created a new race called "Mustang vs. Beetle" for a race that I have already had ongoing. How can I create a TBrace for these? It wouldn't let me create a race that started in the past and I am not sure where it got the dates that it is showing for this race now (which starts in the future). Is there a way for me to modify the dates and add my 2 TB's that are already racing?