I helped develop a web app used by major drug companies in 2001 that's still in use as far as I can tell. Marvel at the Dreamweaver-enabled design: https://resultview.q2labsolutions.com/resultview/logon/logon...

:-) Nice.

The oldest web app code of my own that I still maintain/evolve turned 20 this year, so yours is older than mine. I think it's largely a Ship of Theseus at this point, though I did just remove some code the other day that was absolutely untouched since 2008.