On 11-5-2018 18:31, Adriano dos Santos Fernandes wrote:
Hi!
Here is the first README version for the time zone feature.
https://github.com/FirebirdSQL/firebird/blob/work/time-zone-support/doc/sql.extensions/README.time_zone.md
Reading through that, a few questions:
# About the 2 bytes for the time zone identifier or displacement
What is the valid range for displacement? Is it -12:00 - +14:00 (see
https://en.wikipedia.org/wiki/List_of_UTC_time_offsets) or something
else? If so, why the +1439 in the calculation of the byte value? It
seems to me the current possible range for the byte value is 719 - 2279
(-12 * 60 + 1439 = 719 to 14*60 + 1439 = 2279).
The choice of 1439 seems to suggest an expectation of -23:59 - +23:59
(or 0 - 2878), why?
Will Firebird guarantee that the timezone identifiers will be stable
(that is: a timezone will not get a different id in a new version or ICU
release?), or would a driver always need to query the table with time
zones instead of keeping its own list?
# Set time zone local
What does this mean? Does it mean set to server time zone?
# Time zone identifiers
How are ambiguities handled:
For example:
Which time zone is ACT (id 65534)? Is it Acre Time (-05:00) or
Australian Central Time which is an alias for ACST/ACDT (+09:30 / +10:30)?
Which time zone is IST (id 65024)? Is it India Standard Time (+5:30) or
Irish Standard/Summer Time (+01:00) or Israel Standard Time (+02:00)
And what about AST (65530), BST (65162), CST (65154), PST* (64988)?
Interestingly a number of duplicates (according to
https://www.timeanddate.com/time/zones/) are not included in the list:
ADT, AMST, AMT, CDT, GST, PYT, WST
I notice that 'summer' time zones are not present. For example, CET
(Central European Time, +01:00) is present, but CEST (Central European
Summer Time, +02:00) is absent. Does this mean that CET represents both
summer and winter time?
* PST is Pitcairn or Pacific, with the same offset, they are considered
different time zones
--
Mark Rotteveel
------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
Firebird-Devel mailing list, web interface at
https://lists.sourceforge.net/lists/listinfo/firebird-devel
