Once in a blue moon
Once in a blue moon
on a very rare occasion, rarely, seldom, scarcely, intermittently, once in a while, irregularly, now and then, not often
It happens once in a blue moon that a man changes his life through his habitual reasoning. No matter how fully he may sense the new plans and aims revealed to him by reason, he continues to plod along in the old paths until his life becomes frustrating and unbearable… he finally makes the change only when his usual life can no longer be tolerated.
Source: https://onejourney.net/
Antonyms: often, frequently, regularly
Farsi: گهگاه، به ندرت