[Interest] Relashionship between time_t and QDateTime

[Calogero Mauceri]

On 8/27/2013 11:01 PM, Constantin Makshin wrote:
> The original Calogero's message mentioned a file from December 2007, a
> date outside of DST (unless there's a country that uses DST during
> winter). Now it's August, so the DST is active and during "UTC -> local
> time" conversion Windows adds that 1 hour Calogero is seeing. DST gets
> incorrectly applied because it's active at the moment of conversion,
> although it wasn't used at the moment the original timestamp represents.
>
> I bet that the problem will go away when DST ends [again]. :)

I think Constantin's analysis is correct.

Just for your information, I'm using Qt 4.8.4. The machine where I 
noticed the problem is running Microsoft Windows Server 2003.
The Time Zone is set to (GMT-05:00) Eastern Time (US & Canada), in DST 
currently.

Let me know if you need any additional information
Calogero


>
> On 08/27/2013 11:42 PM, Thiago Macieira wrote:
>> On terça-feira, 27 de agosto de 2013 22:59:44, Constantin Makshin wrote:
>>> Windows can store information about daylight saving transitions for past
>>> years, but always uses one for the current year. And since daylight
>>> saving transition dates and time tend to slightly drift from year to
>>> year, there's absolutely no guarantees of getting correct time
>>> conversion results; in general case 1-hour error is nearly inevitable.
>>> If you're on Windows, either calculate and apply DST yourself or forget
>>> about correct "UTC <-> local time" conversions.
>> This is not about the corner case of a file that was created in the hour of the
>> transition, or even in the week that shifted between non-DST in one year to
>> DST in another (or vice-versa).
>>
>> >From what I understand, we're talking about a file created in DST and checked
>> outside of DST (or vice-versa) in the *same* *year*.
>
>
> _______________________________________________
> Interest mailing list
> Interest at qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest

-- 
Calogero Mauceri
Software Engineer

Applied Coherent Technology Corporation (ACT)
www.actgate.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.qt-project.org/pipermail/interest/attachments/20130828/e7b0ff4e/attachment.html>