In one of Kanzenshuu’s features they analysed the evidence surrounding the debut date for Dragon Ball Z in North America in 1996, which has many caveats to say the least.
Unlike the UK where we can definitively say Funimation’s dub of Dragon Ball Z premiered on March 6, 2000 on Cartoon Network or Finland where it was January 15, 2003 on SubTV the US is a completely different ballgame since the show did not premier on a mainstream channel, but instead it was smaller regional networks.
Long story short, it depended on the state, and while the formal, widespread premier was on the weekend of September 14th-15th there were smaller, more niche weekday sneak peaks for the weekdays of September 12th and 13th, although anecdotal evidence suggests there may have been an earlier weekend sneak peak on September 7, 1996.
Take this blurb from the September 14-20, 1996 issue of TV Guide in the Kids Programming Fall Preview:

In only one known instance does a fan online suggest that this September 7th debut happened:

There are no known newspaper listings that confirm Dragon Ball Z was premiered on any channel this date, that is not to say it didn’t happen, as TV schedules can sometimes be ambiguous, a TV block can be listed but not the programmes, in the case of syndicate networks the schedules might list “Local Programming”, which according to a fan on the Kanzenshuu forums can be anything from sitcom reruns to church broadcasts to bootlegs of a pay per view wrestling event.
So it is possible, although it may never be known for sure whether or not Funimation’s English dub of Dragon Ball Z first aired in North America on September 7, 1996, but nonetheless the week up to September 14th did include sneak peaks, as Kanzenshuu’s article highlights.
In any case this week celebratory threads and articles can be expected, just as was the case for the 20th anniversary of this dub in North America on both forums and websites.