[tz] Incorrect Time Zone Data for American/Grand_Turk

[Robert Elz]

    Date:        Fri, 3 Aug 2018 13:10:15 +0100
    From:        Jon Skeet <skeet at pobox.com>
    Message-ID:  <CA+5fHtL1aMO2e_oBoj4QGEHmJvYJ1-uykXDb2r4a=kVkzw+=uw at mail.gmail.com>

  | For example, my code to determine transitions got stuck [...]
  | because multiple UTC instants end up mapping to the same local time

If that is a problem for your validator, then you need to fix it, as that
kind of thing can easily happen, whatever the codebase is.

Simply consider what would happen if Kiribati decided to swap back to
the other side of the date line (revert to its previous zone offset).
There would be almost an entire day of duplicated local times (some
date would repeat in local time, more or less - either that or there
would be an "invented" day (Feb 29 in a non-leap year or April 31 or
something similar, which would cause even bigger problems.)

kre