10.05.2018 22:08, Adriano dos Santos Fernandes wrote:
On 10/05/2018 15:30, Vlad Khorsun via Firebird-devel wrote:
The key is that DST doesn't affect given time zone. TZ could be
"standard time" based (such as MSK)
or "DST based" (such as MSD or IST you speak about) but TZ itself is
not changed with DST start\end.
What is changed - is what TZ should be used. But we (I) speak not
about it.
That only in this scheme you linked, that is un-mappable to computers.
This scheme also has invalid date/tz.
To convert a timestamp to UTC I need to known the timestamp and its
timezone.
So, I can't convert 2018-05-01 00:00 BRST (Brazilian Summer Time) to
UTC, as there is no summer time in 2018-05-01, only standard time.
And 2018-01-01 00:00 BRST + 4 months will not change to BRT (Brazilian
Standard Time).
This scheme just does not work!
On the other hand, I can convert any timestamp in America/Sao_Paulo to UTC.
To do it, you need to know TZ (or, offset from UTC) used at America/Sao_Paulo
at given moment, isn't is ? And this offset is also depends on given moment
itself. And in different moments there could be different offsets.
Correct ?
I can add any interval to any America/Sao_Paulo timestamp and it will be
already an America/Sao_Paulo timestamp.
In fact the arithmetic is very simple, just add the interval to the
stored UTC timestamp.
When converting back to a string representation, it will be showed in
America/Sao_Paulo time.
It is very good (while have no answer on "versioned" time zones question).
Could you answer my question below ?
Please, convert to UTC and explain how to do it:
2010.03.01 04:00 Europe/Moscow,
2013.03.01 04:00 Europe/Moscow,
2016.03.01 04:00 Europe/Moscow
Regards,
Vlad
PS It seems i start to understand you - you want to say that rule for
given area (full TZ name ?) describes all possible moments when offset
from UTC is changed. Including DST start\end and changes due to political
reasons. Correct ?
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