on this occasion (which is in contrast to what happens usually) 仅此一次（与通常情况对比而言）
Just for once he arrived on time.
只有这一次他按时到了。
Can’t you be nice to each other just this once?
难道你们就不能彼此客气哪怕一次？
on this occasion (which is in contrast to what happens usually) 仅此一次（与通常情况对比而言）
Just for once he arrived on time.
只有这一次他按时到了。
Can’t you be nice to each other just this once?
难道你们就不能彼此客气哪怕一次？