The earliest check-in on Foursquare I have is January 2010. You can see it here - https://www.spudooli.com/recently/2010-01-12

I've had that app on my phone and used it at least once every single day for the last 14 years. I contributed a lot of content to them, venues, check-ins, photos, tips.

And then about 10 days ago they removed my API access for reasons I have no idea.

So tonight I coded my own check-in solution. Replaced them completely in about 85 lines of python and html.