Methods to calculate zero hour:
Sphynx - how long is a piece of string?
Aurilio Peccei (Limits to Growth - "What we need (now) is to learn what it takes to learn what we need to learn, and learn it". which was so succinctly summarized by Donald Trumsfeld in The Known/Unknown - Knowns/Unknowns matrix.
The real solution is in Zeno's apocryphal paradox of Achilles and the tortoise in which Achillies chases a tortoise with a 100 metre start, halving the distance every 10 seconds (well it was quite a fast tortoise).