If we leave with no deal, then negotiation is unlikely to stop and depending how the UK and EU are affected will change the power dynamic of the negotiations. Without a crystal ball, I can't give any time scale, but I believe in order for trade to be facilitated, certain things will be overlooked or waved through initially if needed and then tightened up on. I can't see there being a defining moment or date as such, just agreements made as the tangible issues arise and thus targeted. Currently, no one can say with certainty what will happen a day, a week, a month, a year out from a no deal, it needs to happen for this to occur. Then action taken in response.