[tz] Incorrect Time Zone Data for American/Grand_Turk

Robert MacGrogan rmacgrogan at flightbridge.com
Thu Aug 2 16:23:50 UTC 2018

Sorry, I was out of town for a bit and was unable to respond.

FYI, I'm using a .NET library that is backed by the time zone database.
Specifically I'm using my own branch of this:


I installed the 2018e data myself so there is no distributor involved. I
suspect that some will think that the problem must be in the code base. I
think that's unlikely because the code base has not changed in years and
works perfectly except for this one time zone.

I'll see if I can run the test you suggest, but I don't currently have a
Linux or Unix install handy and that looks like Unix to me.

Running my own unit tests, btw, that is not the output I get. For Sun Mar
11 07:00:00 2018 UT using the 2018e data I get  Sun Mar 11 02:00:00 2018 as
the local Grand Turk time. So maybe it is a code issue. If I change line
3426 in the northamerica file to this:

-4:00 US AST 2018 Mar 11 3:00

I get the correct result.

On Tue, Jul 24, 2018 at 12:56 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

> On 07/24/2018 08:00 AM, Robert MacGrogan wrote:
>> I'm definitely seeing incorrect behavior when I test dates in July of
>> 2018.
> How exactly are you testing that? Are you using the data installed by your
> distributor, or the actual 2018e data?
> What happens when you do this from tzdb 2018e source?
> rm -fr /tmp/tz
> make clean
> make TOPDIR=/tmp/tz install
> ./zdump -Vc 2018,2019 America/Grand_Turk
> Here's the output that I get. If you get something different, please
> investigate.
> America/Grand_Turk  Sun Mar 11 06:59:59 2018 UT = Sun Mar 11 02:59:59 2018
> AST isdst=0 gmtoff=-14400
> America/Grand_Turk  Sun Mar 11 07:00:00 2018 UT = Sun Mar 11 03:00:00 2018
> EDT isdst=1 gmtoff=-14400
> America/Grand_Turk  Sun Nov  4 05:59:59 2018 UT = Sun Nov  4 01:59:59 2018
> EDT isdst=1 gmtoff=-14400
> America/Grand_Turk  Sun Nov  4 06:00:00 2018 UT = Sun Nov  4 01:00:00 2018
> EST isdst=0 gmtoff=-18000


Rob MacGrogan | Director of Software Development
rmacgrogan at flightbridge.com  <rmacgrogan at flightbridge.com>

[image: FlightBridge] <http://www.flightbridge.com/>

FlightBridge, Inc.
530 Means Street, Suite 405
Atlanta, GA 30318
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