Ask HN: What is the oldest code you wrote that is still running in production?

I'm curious to hear from both folks that have been in the industry for decades and those that are still relatively new: To the best of your knowledge what is the oldest bit of code that you've written that you know (or believe) is still running in production?

For myself: I wrote a data management system for nuclear reactor steam generator inspection/repair in VB6 from 1997-1999. It has been running in production since then.