Shìguòjìngqiān zhīhòu, tā duì nà duàn wǎngshì yǐjīng shìrán le.
Once enough time had passed, he made peace with that chapter of his past.
Tips
history
Attested in the late-Qing novel 《黄绣球》 (Huang Xiuqiu, 1905) by Yi Suo (颐琐): 黄绣球与黄通理事过境迁,已不在心上 — 'For Huang Xiuqiu and Huang Tongli the matter was past and the circumstances changed; it no longer weighed on their minds.'
usage
Often used to argue for letting something go. Common collocations: 事过境迁了 (it's all in the past now), 事过境迁之后 (once enough time has passed).