Help find an old post about someone analysing geolocation data

hello, I just remembered reading a blog post on HN with someone analysing geolocation data from his phone and his wife's phone to check if they had ever bumped into each other before actually meeting and getting married.

I know it is very vague and highly improbable, I tried to use the search feature but had no success so far. does someone happen to know what I am talking about ? thanks !