In our place, it takes at least a week to get them all done. We start with the living room, kitchen and hallway. That means that sometimes the back of the house is on a different time to the front of the house as we're always rather loathe to rush into someone's room just to fix the clock. So it might be the next day - or even the day after that if we forget.
It all adds up to a lot of confusion for the entire week. Particularly if we changed the microwave, but not the cooker, atop which it sits.
One of our guests told us that they never pay attention to any clock in the room, or anywhere else (not even in your car??) because they use their phone. This worries me as iPhone has demonstrated on a regular basis over the last 10 years, that there is always a glitch that needs to be fixed - they are not perfect. I mean, even Big Ben loses a second or two every year or so. Imagine British trains not running on time, heaven forbid!
This pretty little clock sits outside the London room and is usually correct, except, perhaps on the night we're supposed to change the clocks, in either direction - and completely forget. So, as you've finished reading this, get up - and go turn all your clocks back one hour!