The seven-day week has no astronomical basis.It does not align with the moon, the sun, or the year.Governments tried to replace it with systems that made more sense.They failed every time.Revolutionary France imposed a ten-day week to optimize labor.The Soviet Union reorganized time itself to keep factories running continuously.Both systems collapsed.The reason was not math.It was coordination.The seven-day week survives because it synchronizes rest across entire societies.Efficiency fractures. Shared rhythm holds.Time did not shape the week.The need to coordinate did.