Voted Best Answer
Feb 22, 2021 - 06:23 AM
As we point out quickly in the corresponding tutorial, this is one of these expressions where English and French differ.
If we're referring to something happening now in French we need to use the present tense, while in English this expression triggers a present perfect, so:
This is the first time that I've seen them = C'est la première fois que je les vois
We would only use the past tense in French if we're referring to something that happened in the past, as in:
The first time that I saw them was for your wedding = La première fois que je les ai vus, c'était pour ton mariage