N64 Zelda patent expired today

I happened to be looking through some N64 technical documents including a list of patents[1] and noticed that many of them seemed to have expired today!

including ones related to:

Z-buffering[2]

Starfox 64[3]

and Mario 64[4]

[1]: https://forums.cen64.com/viewtopic.php?f=16&t=7

[2]: https://patents.google.com/patent/US6414678

[3]: https://patents.google.com/patent/US6540612

[4]: https://patents.google.com/patent/US6331146