How to clean the house before New Year 2027?

Are you talking about leaving everything for three days before or even for New Year's Eve itself? If that's the case, the way to go is to start from top to bottom (ceiling, fans, shelves) and from inside to outside of the rooms, because dust falls and you don't want to clean a spot twice. Then wipe down surfaces with a damp cloth, beat the rugs, and do the floors last.

For that musty smell that sticks around, open the windows wide during the day and let the sun hit directly the corners where it's more closed off. A product that actually works is diluted bleach (one part to ten of water) applied with a cloth on wall corners, baseboards, and under furniture - kills the mold. After that, put a container with baking soda or dried brewed coffee (yeah, coffee) in a corner of a cabinet or under the bed, which absorbs the leftover smell way better than those shelf air fresheners.

Let me ask you this: are you talking about one or two weeks before, or are we really talking three days? Because that's a huge difference.

I learned the hard way that if you don't want to go crazy on the 30th, the real secret is starting back in the second week of December. I make this kind of ridiculous schedule, but it works: Monday I tackle mold, Tuesday is fridge and cabinets day, Wednesday and Thursday we focus on windows and mirrors. Friday is the full bathroom. I save the floors and big pieces for last because those are the things that get dirty again the fastest.

About that moldy smell that won't go away: what works for me is making a solution with white vinegar and water (like 1 part vinegar to 3 parts water) and going over every dark corner, under furniture, behind doors. Then I leave the fan on or open the windows wide. Anti-mold boxes also help, I put one in each main room. The smell goes away, but it takes a few days.