When can pigs fly?

When pigs fly

Something that will never happen; it's impossible or extremely unlikely.

Similar idioms –

• Not in a million years

• Don’t hold your breath

Examples

1. He said he’d clean his room every day—when pigs fly!

2. I’ll trust her again when pigs fly.

中文意思是 – 不可能發生的事、天方夜譚 / 不可能发生的事、天方夜谭