The TIME GAIN concept is a personal concept that I invented in 2008 in order to use it as the successor of the real GDP growth concept. It is based on three main assumptions. The first is that it is useless to have money but nothing to buy with. The second is that an individual may someday change, a group of individuals never. The third is that our physical world is a finite and seriously damaged world.TIME GAIN needs to be thought as the expression of the additional future time for economic and social life that the implementation of sustainable rules like the ‘one child per woman’, ‘no massive immigration’, ‘traveling only on cargo ships, trains, lorries’, and ‘sparing, reusing, repairing, and recycling every item’. I calculated TIME GAIN by 1) setting a rule of three relationship between total GDP quantities and oil consumption time (equal to each country’s share of the oil RESERVES/PRODUCTION ratio which shows the number of years left for similar national and international consumption), 2) by adding or deducing every new annual oil consumption time to or from the total of annual oil consumption years and, 3) by deducing the sum from calendar time. The difference would be the NATIONAL TIME GAIN value.