also: くじ
noun
past events; bygones
Refers to things that happened in the past, often with a nuance of being over and done with. Can be used in expressions like 旧事を忘れる (forget the past).
旧事をいつまでもくよくよ考えても仕方がない。
There's no point in brooding over past events forever.
彼は旧事を水に流して、新しい人生を始めた。
He let bygones be bygones and started a new life.
Compound of 旧 (old, former) and 事 (matter, thing). The reading きゅうじ is the standard on'yomi, while くじ is a less common variant reading.