First, I think it is great to have another day after IMLD to continue to think about, discuss, and do something with and for diverse languages. GCLR apparently picked the date with something like that in mind. IMLD and GLAD22 contrast with and also complement each other, which may potentially be very positive if the new observance continues.
Another difference is that while IMLD, which has been observed annually for over two decades now, is truly international, GLAD22 - its first year - apparently had no activities in or relating to Africa. One imagines this will change before a second Language Advocacy Day, but this lacuna is the main reason that I wanted to post about GLAD22 on Beyond Niamey (watch this space?).
Finally, at the risk of oversimplifying, it seems that IMLD is mainly for the speakers, and GLAD22 is largely for allies. The former is essential, and the latter is important - in some cases perhaps critically so - but also tricky.
Advocacy - and I accept that I would fall into the category of an advocate, for the work I've chosen to do relating to African languages over the years - can ideally help positive change. The down side of advocacy, as I see it, is the potential for bringing one's own agenda, personality, and even misunderstandings into others' space. That's especially problematic when there is a difference of power (position) of the advocate and those s/he advocates for. (In international development, for example, I've noted the dynamic where outside experts effectively dominate all positions in a discussion about others' way of life.)
Which is not to argue against advocacy, but rather to advocate (!) both for awareness of the contexts in which one is advocating (e.g., the power differential) and for as deep a familiarity as is possible with the realities of those (or that) for which one is advocating. (I'm still thinking about this particular set of issues.)
In any event, hopefully Global Language Advocacy Day will develop in a positive way, connect with Africa, and complement IMLD.
Also, it is perhaps not coincidental that GLAD22 was initiated in this, the first
year of the International Decade of Indigenous Languages (IDIL). So one also hopes for constructive synergisms of effort and effect there as well.