One's fated time has come to an end; one's days are numbered, often implying death.
老先生常说，人生有定数，当他感到身体日渐衰弱时，便知岁在龙虵，坦然面对。
The old gentleman often remarked that life has a fixed course. As he felt his body gradually weakening, he knew his fated time had come and faced it with serenity.
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