[tz] [PROPOSED] Use "PST/PDT" for Philippine time

[Paul Eggert]

Michael H Deckers wrote:

>     My second point was about the abbreviation "PDT", as proposed
>     for Manila summer time (which you have called "invented"),
>     not the abbreviation "PST" (which you have not called
>     "invented" in your proposal).

Ah, sorry, I misunderstood. With "PDT" I was attempting to follow this guideline 
in theory.html:

>     Use a consistent style in a tz region's history.
>     For example, if history tends to use numeric
>     abbreviations and a particular entry could go either way, use a
>     numeric abbreviation.

Since most Philippine history used an alphabetic abbreviation, I thought it 
better to do so with daylight-saving time too. This is consistent with Hong 
Kong, Taiwan and Korea, all of which have "JST" for time during Japanese 
occupation because they use alphabetic abbreviations now, and it is in contrast 
to other locations that use "+09" for timestamps under Japanese occupation.

We have competing guidelines here: "be consistent" and "don't invent 
abbreviations", and it's a judgment call as to which is more important.

PS. Many of those "+09"s are sheer guesswork by Shanks, but that's a different 
story....