〜を機に

Marks an event (retirement, marriage, moving, an illness, an incident) as the trigger for a deliberate change in the following clause. It is formal and typical of written Japanese and speeches; the second clause usually describes a conscious decision or a lasting change, not a one-off trivial action. 〜をきっかけに is the everyday equivalent and can take negative or accidental triggers more freely.

• 結婚を機に、たばこをやめた。

  けっこんをきに、たばこをやめた。

  I quit smoking when I got married.

• 定年退職を機に、夫婦で田舎に移り住むことにした。

  ていねんたいしょくをきに、ふうふでいなかにうつりすむことにした。

  Taking his retirement as an opportunity, the couple decided to move to the countryside.

• 今回の事故を契機に、安全対策が大幅に見直された。

  こんかいのじこをけいきに、あんぜんたいさくがおおはばにみなおされた。

  The recent accident prompted a major review of safety measures.