noun
age forty; past forty; the age of discretion
Literary or formal term for the age of forty, originating from Confucius's saying that at forty one is no longer perplexed. Often used in congratulatory contexts or to refer to middle age with a sense of maturity.
彼は不惑の年を迎えた。
He reached the age of forty.
不惑を過ぎてから新しい趣味を始めた。
After turning forty, I took up a new hobby.
From the Confucian Analects: 四十にして惑わず (at forty, one has no doubts). The kanji 不 (not) and 惑 (perplexity) combine to mean 'free from doubt', metaphorically referring to the age of forty.