Salad days

Dal libro "101 English idioms explained":
When were your salad days? Maybe you haven't had them yet.
You might guess that salad days are days in the summer when you eat more salad but you'd be wrong. Salad days are a particularly happy time; possibly the best time in your life.

'Ah, I remember when I was working in Australia; those where my salad day.
Have you had your salad days yet?'