We use clocks and calendars to organize all our personal and social relationships and they do a very good job. We are not always on time for our appointments, but we know when we are early and when we are late.
The same cannot be said about money. We need money for most of the things we need to live, but we can never be sure how much our money is worth. To make matters much more complicated, there are over 100 national currencies being used in the world today and none of them, zero, state on the money itself what the money is worth. The name of the money tells us its nationality but not its value.
By denominating money in Hours of work and by trading an hour of my time for an hour of your time world wide, we can trade fair to everyone's benefit. That is how we can get to world peace.