To follow up on my previous mention of the topic, here is an image that illustrates the problem:


(image available online at http://OnTimeZone.com/images/baja.gif)

I contacted an established business on the island and confirmed they observe Pacific time, not Mountain.  As I mentioned previously, the time zone border in the area follows the border between Baja and Baja Sur, which at that point runs directly east/west on the 28th parallel.

I had noticed that some maps (e.g. here.com nee navteq, http://here.com/27.8912314,-114.8358911,10,0,0,normal.day) show a ferry running between the island and Bahia Tortugas on the mainland in Baja Sur (which observes Mountain time).

I confirmed that the ferry does not, indeed, exist.  My contact had never even heard of it. 

So a pure guess is that when the CIA first drew the map, the ferry was in existence and led to the island observing Mountain time - possibly unofficially, who knows - and that when the ferry went away the economic tie to Baja Sur went away with it, and the island (now served commercially only by air) reverted to Pacific time.  I have no evidence to support that guess.

I bring this to the attention of the list just in case this needs to be further investigated and to ensure that any history in the TZ db related to the affected area is accurate.

Regards,

Steve Jones, St. Louis, MO