The Scalable Vector Graphics image format (SVG) became a W3C Recommendation on 2001-W36-3, or as the cool kids are calling it, 2001-06-05. (Some sources say 2001-06-04; my source is W3C's SVG history.) No matter how seriously you're taking the ISO 8601 week calendar, this comic has been released slightly earlier than the actual 20th anniversary.
I got the idea to celebrate with fireworks when I found an early SVG animation from 2001 of fireworks.
(This is not an endorsement for anything the unknown creator of that image has done.)