for old times' sake

If you do something for old times' sake, you do it in order to remember a happy time that you had in the past.

看在旧日的情分上;念及老交情

We should all meet up again - just for old times' sake.

我们大家应该重聚一次——就为了重温美好的旧日时光。

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For old times' sake, I agreed to go with him.

看在旧日的情分上，我同意和他一起去。