On Thu, Feb 21, 2019 at 10:12 PM Brian Adkins <lojicdot...@gmail.com> wrote:
> On Thursday, February 21, 2019 at 9:54:23 PM UTC-5, Jon Zeppieri wrote:
>>
>>
>>
>> On Thu, Feb 21, 2019 at 9:48 PM Brian Adkins <lojic...@gmail.com> wrote:
>>
>>> On Thursday, February 21, 2019 at 9:35:58 PM UTC-5, Brian Adkins wrote:
>>>>
>>>> On Thursday, February 21, 2019 at 9:26:07 PM UTC-5, Brian Adkins wrote:
>>>>>
>>>>> I'm using the (today) function from the gregor library. It was
>>>>> returning tomorrow instead of today, so I thought the problem was the
>>>>> timezone on my Ubuntu server. I configured the timezone to be US/Eastern
>>>>> via: sudo dpkg-reconfigure tzdata
>>>>>
>>>>> Now the date command returns: Thu Feb 21 21:23:43 EST 2019 as
>>>>> expected.
>>>>>
>>>>> Unfortunately, (system-tzid) returns: "Etc/UTC"
>>>>>
>>>>> So, gregor's (today) still returns tomorrow (since it's so late).
>>>>>
>>>>> Anyone know how to get (system-tzid) to return the correct value on
>>>>> Ubuntu?
>>>>>
>>>>
>>>> Some more info:
>>>>
>>>> /etc/localtime is linked as: localtime ->
>>>> /usr/share/zoneinfo/US/Eastern
>>>>
>>>
>>> I reinvoked sudo dpkg-reconfigure tzdata and chose America/New_York
>>> instead of US/Eastern, but I still get the default "Etc/UTC" from
>>> (system-tzid)
>>>
>>
>>
>> Huh. Could you do the following and tell me what you get?
>>
>> > (require tzinfo/private/generics)
>> > (require tzinfo/private/zoneinfo)
>> > (define zi (make-zoneinfo-source))
>> > (zoneinfo-dir zi)
>> "/usr/share/zoneinfo"
>> > (detect-system-tzid zi)
>> "America/New_York"
>>
>
> > (require tzinfo/private/generics)
> > (require tzinfo/private/zoneinfo)
> > (define zi (make-zoneinfo-source))
> > (zoneinfo-dir zi)
> "/usr/share/zoneinfo"
> > (detect-system-tzid zi)
> #f
>
> Also:
>
> $ ls -l /etc/localtime
> lrwxrwxrwx 1 root root 36 Feb 21 21:45 /etc/localtime ->
> /usr/share/zoneinfo/America/New_York
>
> $ cat /etc/timezone
> America/New_York
>
>
Thanks.
Okay, so first I figured that the problem was probably due to the weird way
that I try to discover the target of an /etc/timezone symlink. (Racket
doesn't provide that functionality, as far as I could tell at the time, and
I guess I wanted to avoid the FFI? Even though I used it for Windows? My
memory fails me.)
But, if that method fails, it also tries getting the value from
/etc/timezone, which you noted, is set correctly. And that method of
getting the timezone is really simple. It just reads the file. So... hmm.
Okay, let's do this exhaustively.
1. Verify that (system-type) is 'unix. (Just to make sure we check
everything.)
2. In DrRacket, in the definitions window, put the following:
```
#lang racket/base
(require tzinfo/private/zoneinfo)
```
3. Right click on `tzinfo/private/zoneinfo` and select "Open zoneinfo.rkt."
4. In the new DrRacket window that contains the source of zoneinfo.rkt,
click "Run."
5. Then, in the interaction pane, do:
> (define zi (make-zoneinfo-source))
> (tzinfo-has-tzid? zi "America/New_York")
#t
If this is #f, that would be bad, and you can stop right there.
6. Next:
> (find-zoneinfo-directory default-zoneinfo-search-path)
"/usr/share/zoneinfo"
If you don't get the same values for this, that would be odd.
7.
> (detect-tzid/unix (zoneinfo-dir zi)
(find-zoneinfo-directory default-zoneinfo-search-path)
(tzinfo->all-tzids zi))
"America/New_York"
I expect you'll either get #f here or else you'll get a string but it won't
be a valid IANA time zone name.
8. Near the top of zoneinfo.rkt, you'll see a require line for
"os/unix.rkt." Right click that and open the file. Run it.
9. In the interactions pane:
> (tzid-from-env)
#f
(If this isn't #f, and it also isn't an valid IANA time zone id, that would
be the problem.)
10.
> (tzid-from-/etc/timezone)
#f
Based on what you wrote above, I expect you to get "America/New_York" here.
(I get #f, but I'm on OS X.)
===
I think you'll have to get unexpected results from one of these, and that
should help us figure out the problem.
My best guess right now is that detect-tzid/unix will return a string that
isn't a valid IANA tzid. And that might be because you have the TZ
environment variable set.
Thank you for helping me track down this bug. If my guess is correct, I
need to make a slight change to the code.
(Summary: detect-tzid/unix tries a few different methods for determining
the system time zone, and it stops when any one of them is non-#f. But the
returned string is only validated against the list of IANA zones
afterwards, so if any of those methods returns a string that isn't a valid
time zone, it won't try any of the other methods.)
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