Once in a blue moon these works even make money.
The blue moon was well over to the west, above the sea by now.
Every once in a blue moon we find evidence there is a God.
However, the opportunity to actually use them might come up only once in a blue moon.
So now he just comes round once in a blue moon.
If you would visit your mother once in a blue moon, we could eat together.
Said he'd send money home, which he did once in a blue moon.
Every once in a blue moon, he'll get the chance to perform himself.
Once in a blue moon the addressing system itself changes.
Not everyone on Earth will see the two blue moons in 1999.
Słownik astronomiczny