at 11:48am
I was suspicious about this. I'd checked RSBN's YouTube hours before noon 1/20, and their broadcast was scheduled to go live at 11:55. When I checked back just before noon, the video was missing from their page.
I didn't waste an instant on surprise. Fortunately by looking for another video to watch I came across RSBN's live video in the related videos section. It was 11:59am and Biden was speaking.
I had to watch awhile to realize he must have already been sworn in.
I'm making the point that it wasn't just me that assumed the time for swearing in was at noon. The news site that put out Trump's rallies and speeches when nobody else did thought 11:55am was a good time to start broadcasting. So a lot of people who most would have scrutinized Biden's swearing in missed it. (They could look up the recording of it later, but what percent would?)
Well, this forum became more entertaining since yesterday. The salt from the left will be immense once everything is out in the open!