Well I started this in the beginning of October but had to travel for business so I didn't get a full month of data. But still, I did get a good bit of information.
Each watch was calibrated for altitude before the test began. I was amazed with the accuracy of the Nike and the Core. Before you all get wadded up, you must understand that ALL of these ABC watches have issues with "barometric drift".
A few more notes on the test... this test was done when my house had its windows open and the watches spent most of their time on my night stand next to an open window. The only exception being my Core... I wore that a LOT during the test... That means many trips to and from Atlanta (about an hour away) and many trips in and out of large office buildings etc... That makes its accuracy even more impressive in my opinion. Note that the Yachtsman does not have an altimeter, and the Observer never moved because the altimeter was locked