Hi

Most (as in the center of the distribution) afordable  watches are calibrated 
to run fast. 
There is info on this in the archives. A pretty typical target is 10 seconds a 
month.  Yes,
we used that as a target back in the 70’s but it’s still pretty common. You 
have to get 
lucky to find one that is dead on time. 

Some math:

2,592,000 seconds in a month. 1 second is about 0.4 ppm.

Your typical watch crystal moves about 20 PPM over 0 to 50 C. 

The curve is a parabola with a tolerance on the inflection point.

So 10 seconds a month comes out to around 4 ppm. With the temperature out 
around 
20 ppm, you need a fairly stable / consistent environment to hit even that sort 
of number.

Yes, you could play compensation games, but doing so only works to the degree 
that
the crystal matches some ideal curve. ( = you get a pretty limited gain with 
low cost crystals
and no testing). 

Bob

> On Mar 6, 2018, at 3:02 PM, al wolfe <alw.k...@gmail.com> wrote:
> 
> My Timex Indiglo looses about a second a month. I think that's pretty good
> for a <$30 watch I got at Walmart.
> 
> Al
> 
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