Terry Pratchett, Strata (1981)
From Strata:
How rich is Kin Arad, daughter of the genuine Earth and author of Continuous Creation (q.v.)? The Company paid its servants in Days, but since they could earn far more than a Day in a day, they often sold surplus time for more traditional currencies. Temporally, then, her account showed that she had another three hundred and sixty-eight years, five weeks and two days in hand, plus one hundred and eighty thousand credits – and a credit is worth a credit these days. In any case, credits were backed by Days.
The galaxy had rare elements in plenty. The transmuter at the heart of every strata machine or dumbwaiter could make anything. What else but longevity itself could back a currency? Kin could buy life. Could Solomon have done it? Could Cloritty have done it? Could Hughes have done it?
She was rich.
