I saw her one afternoon last week.

我在上周的一个下午见到了她。

《牛津词典》

One afternoon, I got bored and actually fell asleep for a few minutes.

一天下午，我感到很无聊，实际上有几分钟还睡着了。

《柯林斯英汉双解大词典》

One afternoon, an old dog ran into Ben's yard.

一天下午，一只年迈的狗跑进本的院子里。

youdao

For example, one afternoon a group of writers and critics gathered to discuss book sales in the Arab world.

VOA: special.2009.03.11

And I went to go visit my sister one afternoon

有一天下午，我去找我妹妹。

从朋友到恋人 - SpeakingMax英语口语达人

Don't forget sections start tonight at seven o'clock and there's another set at eight o'clock and then Friday afternoon at one thirty and Monday morning.

别忘了课后讨论会今晚七点开始,还有几场分别在今晚八点,周五下午一点半和周一上午

耶鲁公开课 - 聆听音乐课程节选

Vivian bought a pack of Parliaments on her way home from school one afternoon.

NEWYORKER: Temporary

Pierre Omidyar was 31 years old when he became a billionaire in one afternoon.

FORBES: Pierre Omidyar: "Ridiculous Rich", And Giving It All Away

Then one afternoon at a student meeting, the Dean addressed this issue head on.

FORBES: A Place of Excellence