When you think about it, people always ask for absolute estimates. How long is it going to take to fix my car, when can I have it? And they are not happy when you say between 1-4 hours or 2-3 weeks. They need one absolute number, and some don’t even care if it’s right or wrong. They just need that number or date or timing. But is there such a thing as absolute measurements? Let alone absolute estimates? If you come to think about it, what we call absolute units of time (or size, length, mass for that matter) are just conventions.