If things get that nuts many won't have power and we'll all have a lot to get done during the day. I'd say that those of us who are knowingly actively manifesting will probably be spending a great deal of time in the evenings especially focusing our intent. There aren't too many things you can do by candlelight, kwim? I don't *think* we need a special day...every evening would be good for most as well as throughout the day as you work.
I imagine if shtf that most of us will be driven to do this all the time.