Time has categorical varieties: each gravitational field in the

cosmos has a different time varying according to mass. On earth at the same instant of celestial time, no two spots really have the same relation to the sun despite our useful convention of time- zones regulating the regional concordance of clocks. When we define duration by span, the lives of men and the lives of other creatures obey different durations, and the durations of artifacts differ from those of coral reefs or chalk cliffs, by occupying different systems of intervals and periods. The conventions of language nevertheless give us only the solar year and its multiples or divisions to describe all these kinds of duration.

George Kubler: The Shape of History

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