Où is a relative pronoun that can also mean "when". That doesn't necessarily mean that everytime you use où in French, "when" is the best way to translate it in English, however.

For example: La semaine où ils sont restés à l'hôtel... -- The week they stayed in the hotel...

In this example, you wouldn't ordinarily use "when" in English, although you could.

Here is a page with some more detail: https://www.lawlessfrench.com/grammar/relative-pronoun-ou/