one day(过去或将来)某一天
例句：I am sure he will succeed one day or another.我确信某一天他会成功的.
some day 将来有一天
例句：I can come back to my hometown some day.总有一天我会回到家乡.
one day与some day都可作“某一天”解,但两者的用法有所区别.one day:on a day(past or future) some day:on some day in the future 意思也就是说,one day既可指过去,又可指将来;而some day只能指将来
the other day 前些日子,前几天,那天
例句：I'm sorry about the other day.前几天真是很抱歉.
the other +表示时间的名词通常只与过去时态连用.