My mom always did a thorough house cleaning on New Year's day. I followed that tradition to some extent, but I do mine before now, a gaijin version of Osoji.
This year, my Osoji took approximately 28 hours (over two and a half-days). I have a three-bed room, one-and-a-half bath house. The cleaning takes so long because it's top-to-bottom and truly involved. Some of the things I do: I pull down the curtains to be laundered, I pull stuff out of drawers, closets, off of shelves, etc. I also pull up the area rugs and move the furniture and scrub and wax the floors. I usually pull a muscle or two as well. I clean the stove, the fridge, change out fire alarm batteries and stuff like that. Wax the woodwork, clean the ceiling fixtures (guess how many dead bugs in my living room light? Too many!) This year, I had the added fun of snaking our bathroom drains. There's some interesting um, stuff(?) that gets built up in those drains. Yuk. I put aside items to go to charity (clothes that don't fit or I don't wear). I take down the Christmas tree and all the other holiday decorations. I also put up our shiminawa and kadomatsu.
As I'm typing this, it's been snowing all morning and it's looking pretty and white outside. My house is sparkling clean and so cozy. Best wishes for the new year!