I think it was early afternoon (well after 11am and before 3pm), January 1st, 2021. My wife and I have a tradition of doing a small photographic expedition on New Year's Day. I think the last time I was there was 2004, and a lot of the buildings were still boarded up by the Navy.
Judging from what gets moored there - you can see the river side from the Vallejo waterfront park and the San Francisco ferry terminal - there is still some fitting out or service work done on largish vessels. I seem to remember at least one (NOAA?) research ship there last year. There is a fair bit of light industry. I think one company making partially prefabricated apartment building modules has a workshop there. Some of the older offices and quarters buildings are preserved/repurposed, and there us a fair bit of residential development. The Touro University campus is on Mare Island.