Learn Spanish (Spain): ¿Cuánto tiempo hace que os conocéis? - How long have you guys known each other?

In Spanish, when an action started in the past and is still happening right now, you use the present tense. English uses the present perfect to say this, which is why it feels tricky to translate word-for-word.

How does the hace que structure work in this sentence?

The phrase ¿Cuánto tiempo hace que...? is a very common formula used to ask how long an ongoing action has been happening. To talk about actions that are still continuing today, you use hace plus the time phrase plus que plus a present tense verb.

Why is os used here, and does it just mean you?

Os is the pronoun for vosotros, the informal plural you used in Spain. While it often just means you, here it acts as a reciprocal pronoun. That means the action goes both ways: you know them, and they know you. So os conocéis specifically means you know each other.

Since the sentence is about knowing, could I use the verb saber instead of conocer?

No, because conocer is used specifically for being acquainted with people or familiar with places. The other verb for knowing, saber, is used for knowing facts, information, or knowing how to do something.