One day means once, at some point, in a story about the past, and some day, at some point in the future. The verb tense shows which: One day I met… is the past, One day I'll… is the future. One day usually comes at the start or end of a sentence.
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One day + past tense (= once, in a story); one day + will / want to / hope to (= some time in the future); on the same day (not in one day)
- One day I missed the last bus and had to walk home in the rain.
- I'd love to work abroad one day, so I'm saving money and learning Spanish.
- One day you'll look back at this interview and laugh.
What changed
First versionMy friend and I started the job in one day.
RevisionMy friend and I started the job on the same day.
To say two things happened on the same date, in one day seems natural. But in one day means within a single day: We painted the room in one day. When two events happen on the same date, the phrase is on the same day: We were born on the same day.
Close by is the other day, meaning a few days ago, very recently: I saw Tom the other day. One day about the past sounds like the start of a story and doesn't say when it happened, while the other day stresses that it was recent.
Your turn
I don't have the money now, but I hope to visit New Zealand ___.
Show the answer
one day — This is about a dream for the future (hope to visit), so you need one day, meaning some day. The other day is about the recent past and doesn't go with a future plan.
Describe a dream you'd like to make come true one day. Name it and one thing you're already doing for it.
One day I want to run a marathon, so I've already started jogging three times a week.
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