Originally Posted by Goldeneye
1/6/1977 may be a possible, but given that it is just a few days after New Year's, is very unlikely, noting the filming schedule for the other seasons, hence eliminating this option.
You noted it is unlikely they filmed that close after the New Year's holiday. I also question the filming date of the pilot as 12/26/1975, the day after Christmas.
I truly enjoy this production guide. I am fascinated with dates, so it is very interesting to me to see when they were filmed.