Thank you for all this info. Most of the time, what I need is a way to keep track of 2 time zones - I travel a lot, and need to know the time where I am plus back home. It seems like the 4th hand plus rotating bezel might be overkill for this. Perhaps a simple 12hr GMT bezel would be best for this.There are a few reasons. Some watches don't have an indep. 24 hr hand, like the Orient GMT. These make use of a rotating bezel/chapter ring to adjust the time difference. Problem with this is you can't tell the time at a glance, just by looking at the position of the hands.
With an indep. GMT hand (any ETA 2893), the bezel gives flexibility. For eg., you can set the GMT hand to UTC time, and rotate the bezel by the given time difference (e.g. +8 for Beijing = counterclockwise 8 hrs). Adjustment is thus instant and easy with very little math required. This is one way to use the bezel but requires the GMT hand to show local time.
Dennis, I think this may be getting a bit too involved for him to follow. I think I made a mistake giving too much info on my previous post/s. Without an actual watch to scenario play-act with, it's rather difficult to visualize.For travels throughout the US, or other small timezone jumps, a regular 12 hour watch with 12 hour bezel might suffice.
For international references, like for making your phone calls, I'd suggest either a pure 24 hour watch with rotating 24 hour bezel (for quick reference and ability to quickly change the second timezone) or a 12hr/GMT watch.
I prefer the first option for a simple reason...If I decide I need to call John Doe in England (currently plus 8 for me) at 1330 his local time, I can just glance at my watch and it makes the conversion for me...I need to call him at 0530 my local.
I use this feature on a daily basis at work to convert zulu-referenced weather prognostics (TAFs) into local times.
The purist Airman models are great for this. I also like the Universal Geneve AeroCompax.