It's not just a day off*--A day off is where we find the time to get the errands and appointments done that we can't fit into a work day. Chores. Anything that counts as a have-to. We might need to wear shoes.
A day to BE rather than to DO.
It is a day to be restored. There's a lot of resting--sleeping in or napping, and just being dozy on the couch. There's quiet and calm.
It is a day for feeding the soul. Beauty and joy and meaning, however we define these things.
Sometimes I sit outside and watch the leaves fluttering in the breeze, the lizards scampering across flagstone. There might be meditation or exercise or hobbies. Other days I read something lovely- poetry or an old favorite... NO manuals, no curricula, none of that. And sometimes it is frivolous and goofy--I will admit that I read three hundred pages of a book with absolutely no redeeming qualities today.
I wear different clothes on my Sabbath. When possible, I stay out of shoes entirely. (Slippers are permissible if the floors are cold.)
Often, I do not leave the house at all on the Sabbath. When I do, it's generally to see a much beloved friend. Occasionally for something fun and quite outside the ordinary.
Sabbath to me, is not unlike shutting off all the accumulated programs and tabs on my computer. Clearing space for what is to come, even when there's some anxiety of "But... I need to deal with that still! What if I forget about it? What if there isn't time?" Bookmark it, baby. It can wait.
*I considered making a Venn diagram of Day Off and Sabbath, but that would definitely count as work.