Can Altitude Affect Accuracy?

I bought this SMPc (with 2500D movement) early this year, when I lived in a Midwest town in the US which has an altitude of 200 meters (656 ft). It ran about 5.5 seconds fast per day while in the U.S.

I recently moved to a city in South America which has an altitude of 2.600 meters (8.530 ft.) and my watch is now running around 0 seconds per day!

So I had the SMPc for about six months in the US where it ran 5 seconds a day, and as soon as I move to South America it gains almost 0 seconds day. Did the higher altitude change this? Perhaps less/more friction in the movement somehow? I know temperature had nothing to do with it because I used it from a cold Midwest winter to hot summer in the U.S and it still remained at +5 secs/day. And right now in South America I am at 13°C (56°F).

I did go through several flight connections and the watch went the the airport metal detector on three occasions, so it might have been magnetized; hence the sudden change in accuracy? I will probably not try to demagnetize it since it is extremely accurate now and don't what to change anything 😀 Just curious why the sudden improvement as soon as I landed in a 2.600 meter altitude city.

Here is a screenshot of the accuracy recorded in May while in the US, and for the past few days in South America.

Was it a sudden change, or gradual? Do you have data from between May and August?
Air resistance (of the balance wheel) goes down with pressure, which could increase amplitude, which could slow down (or speed up; but usually slow down) the watch. I have no idea what fraction of the energy loss of the watch is due to air friction. Maybe Archer knows?
The air pressure change is pretty significant, 25% lower at 2600m.

It was definitely sudden, as soon as I arrived overseas. I check the accuracy of my watch pretty frequently and literally one week ago when I was in the U.S. it was still at +5. The last data I had a screenshot was of late June.

If altitude did affect accuracy to any noticeable timekeeping then there would be serious problems in the vacuum of space...

True, reading a few other threads it looks like altitude would change accuracy to a barely noticeable change only, and not five seconds. So it might have been magnetized while it went through three airport scanners. But wouldn't a magnetized watch accuracy be all over the place?

The movement could also have "settled" in perhaps too (since I wear it frequently) and the movement decided to "settle" in the week I traveled abroad. I bought the watch in Feb. 2020 from someone who bought it at an AD in April 2019, so it was less than a year old when bought. I also know after emailing Omega that the watch was manufactured in April 2011.

About a month ago, I also did drop it from about 1 meter high onto a wooden floor. No scratches/dents and the movement still ran the same.

Whatever weird thing happened, glad it is now +0.2 seconds/day!

If you are high enough you won't care.

Got a genius here! Had not thought about that 😀

This has got me wondering. When I go through airport security, I always leave my watch on so that it doesn't get nicked from the bins (unless they force me to take it off). Could those metal detectors magnetize a watch? I've never noticed a problem; anyone know how they work?

maybe that's what they call "gravitational time dilation"...