That would be today.
And every day, if you're up for it.
The things that change our lives (and the lives of others) are rarely the long-scheduled events, the much-practiced speeches or the annual gala. No, it's almost certain that the next chance you have to leap will come out of nowhere in particular, and you'll discover it because you're ready for it.
Someone to inspire, to connect with, to lead. A system to transform. An idea to share. Responsibility is often just lying around, waiting for someone to take it.