From five o'clock to eight is on certain occasions a little eternity.

从五点到八点这段短短的时间，有时仿佛永无尽头似的。

youdao

For the good on certain occasions we treat as bad, and conversely the bad as good.

因此我们有时将好事视为坏事，反之则将坏事视为好事。

youdao

Maybe you just need to be holding your position at certain moments on certain occasions.

也许你只须在特定的时刻特定的场合坚守你的岗位。

youdao

There are certain occasions in which you first do A and then do B; that's not the same as first doing B and then doing A.

在有些特定的情况下,你先做 A 再做 B,和先做 B 再做 A 是不一样的

耶鲁公开课 - 基础物理课程节选

Now that phrase, "on certain occasions, " carries no phrase of frequently or numerosity.

CNN

"In their letters, there is a lot of emotion and, on certain occasions, a lot of humour, " she said.

BBC: Portrait of Emily Gair Greg and her father's letter

Clinton would wear the small, undetectable hearing aids in each ear only on certain occasions, such as in crowds, his doctor said.

CNN: Clinton Gets A Hearing Aid, Loses A Cyst