one of these days: at sometime in the future“总有一天' e.g. You're going to get into serious trouble one of these days. 总有一天你要倒大霉的。 联想： one of those days:a day full of problems“倒霉的日子” e.g. I'm sure everyone has one of those days and today was mine. 我相信人人都有不顺的时候，今天轮到我了。 one of these days: at sometime in the future “总有一天” e.g. You’re going to get into serious trouble one of these days. 总有一天你要倒大霉的。 联想： one of those days: a day full of problems “倒霉的日子” e.g. I’m sure everyone has one of those days and today was mine. 我相信人人都有不顺的时候，今天轮到我了