Too risky to do crazy shit on the last day, just play it cool and do something you enjoy. Regardless it would be pretty big a historical event to be around when the earth actually gets completely ruined, once in a historytime experience.
I'd get my hair cut and get a new pair of shoes, also I'd probably drink some really good whiskey.
That's the last day right there, if possible I'd have an icecream too, and when the end actually happens I'm going to put on the very fitting REM song just because.
Now I hope y'all don't think I've thought too hard about this, just came up with it all right now, promise. I'm not one of the zombie apocalypse planning dudes, promise, come on... for real...