Learn Spanish (Spain): Hace mucho tiempo que no te veo. - I haven't seen you in a long time.

In Spanish, when you want to say how long it has been since you last did something, you use the formula hace + time + que + negative present tense. Because the state of not seeing the person is still true right now, Spanish uses the present tense no te veo rather than a past tense.

Why do we use hace here instead of desde hace?

When you start the sentence with the amount of time that has passed, you use the structure hace + time + que. If you wanted to use desde hace, you would flip the sentence around and put the time at the end: No te veo desde hace mucho tiempo.

Could I say this without using que?

Not in this exact structure. The word que is the glue that connects the time phrase (hace mucho tiempo) to the action (no te veo). Without it, the sentence wouldn't make grammatical sense.

What happens if I change hace to the past tense hacía?

That changes the timeline. If you say Hacía mucho tiempo que no te veía, it means 'I hadn't seen you in a long time' (referring to a specific point in the past, like when you ran into an old friend yesterday). Because this sentence is about the present moment, we use the present tense hace.