I'll spare you most of the boring details about that fateful first brewday (we tried measuring out yeast nutrient using a scale set to a unit that we didn't know existed,** one of the hoses exploded while filled with hot water, Jared dropped the Official Brewing Spoon, etc.), but the point is that at the end of that day, after we cleaned the trub out of our hair and changed into socks that weren't soaked in wort and chemicals and put ointment onto our various burns, it felt like we had really Accomplished Something. After years of buildout and permitting hell and putting together janky-assed systems*** because that was the best equipment we could afford, we were finally a Functioning Brewery.
And like we do for most of the big moments around here, we took a deep breath and tried to appreciate the gravity of the situation or whatever, but mostly we just looked at each other and said "okay, what's next?"
And that's not to say that we were so focused on Moving Forward that we couldn't stop to smell the roses, but more that we were acutely aware of how every new development had a tendency to add more line-items to our exponentially-increasing to-do lists. We'd set so many things in motion at that point that all we could do was keep moving - we were kind of like sharks, only stupider.
And that's probably why we've never tried to throw a Made Up Holiday around this particular milestone (though we do certainly love making up holidays), because it's essentially the turning point when this turned from a personal passion project into something that we were sharing with The World. That, and we try not to raise a big fuss about brewdays in particular - that's our job, it's just something we do.
* And our sales team, and our delivery team, and our general contractors, and our bookkeepers, and et cetera.
*** Our original brewhouse pumps were SO TINY.