I'm not quite sure what's in my laptop right now but it used to be that there was a separate crystal for time keeping, typically around 32KHz. I believe digita

I'm not quite sure what's in my laptop right now but it used to be that there was a separate crystal for time keeping, typically around 32KHz. I believe digital watches used similar crystals. Those drift a lot less than the high frequency crystals used to generate the CPU clock. Their accuracy is on the order of 10ppm. The other thing that matters is the temperature variation as the frequency will change with temperature. A wrist watch probably sees more uniform temperatures (esp. if it's worn all the time and e.g. has a large metallic backing). Laptops can get quite hot and quite cold. You can get temperature compensated oscillators down to about 1ppm accuracy over a larger temperature range. 1ppm is about 1 second/week. Back in the day I wrote a little utility where every time you adjusted your computer clock it took notice of the drift and fed that back into the time calculation. I.e. it continuously adjusted the clock based on the corrections given to it.