Two important metaphors - Time's cycle and Times Arrow . Judeo-Christian traditions have struggled to understand time by juggling and balancing two ends of a primary dichotomy about the nature of history. Each moment occupies its own distinct position in a temporal series, and all moments, considered in proper sequence, tell a story of linked events in a direction. Fundamental states are immanent in time, always present and never changing. Apparent motions are parts of repeating cycles, and differences of the past will be realities of the future.
Time has no direction.
Significance of the metaphors. Above is my depiction of an open rock cycle. Reservoirs are depicted as yellow boxes, and the processes by which material transfers from one reservoir to another are given in purple. Believe it or not this diagram involves substantial simplification. Trace some paths through it to understand the connections better.