I joke about having to check which Quake birthday it is, but there are actually 3 original release dates for Quake:

1. The Shareware via FTP on June 22nd
2. The Retail release that was shipped to pre-orders on July 22nd
3. The Retail Shareware release via store shelves (and 7 Eleven I guess) on August 30th

Sources:

https://web.archive.org/web/19981203122744/http://www.gamespot.com/features/3dshooter/quake.html

https://web.archive.org/web/20080820131102/http://www.thefreelibrary.com/id+Software’s+QUAKE+hits+retail+outlets+worldwide%3b+QUAKE+and+a…-a018630810