These weren't the first shows of the year, but they were certainly the most significant ones (to that point anyway).
They were make-up shows, Mickey Hart left the band after the first night, the band debuted seven new songs AND each night was a scientific experiment to test a hypothesis about telepathy. The results of the ESP experiments, run by Dr. Stanley Krippner, were published in a peer-reviewed journal, likely the Grateful Dead's first mention in scientific literature.
Here's that article about 'He's Gone' I mention on-air.
Tune in for a Pig-heavy dose of songs from these gigs.