When I originally mentioned the Austin Tea Party, their website listed 2 times: a midday one and an evening one. Checking the Tea Party website, I now see it only talking about the evening event. So I emailed to ask what happened to the midday event.
It seems it is a separate (but obviously related) event, the Don’t Mess With Texas Tea Party.
The evening event is the National Tea Party.
Stuff From Hsoi 
D.C. Gay Tax Day Tea Party – The National Stage
We will be beginning at Lafayette Plaza at 11 a.m. with the “Grassroots” stage and 12 p.m. at the U.S. Treasury Department for the National Stage.
Lafayette Plaza- Grassroots Stage – 11 a.m. – 3 p.m.
Speakers, music, open microphone for public to voice their concerns
U.S. Treasury – Tax Day Tea Party National Stage – 12 p.m. – 2 p.m.
National Stage on Fiscal Irresponsibility