Deborah Pickett schrieb:
Michael Ludwig wrote:
Why aren't the functions specified to use a timezone database and
then work like timezone-aware localtime() in Perl and C?
At a guess, I'd wager that it's the sheer complexity of maintaining a
timezone database that can never be completely future-proofed.
But the OS does that. Of course it can't be completely future-proofed,
but sufficiently so. If some president decides to move his country to
another timezone, where there is more sunlight, he's well-behaved enough
to not make the move overnight, but announce it some months in advance.
And then the word spreads to OS manufacturers, and OS updates work.
Most of the time, at least.
Imagine if every implementation of XSLT 2.0, including embedded ones,
had to grok timezones all around the world.
They can leave the grokking up to the OS. Already, XSLT relies on the OS
feature called "system time" when reading the time and the offset from
UTC. Why stop half-way and not take into account the concept of the
timezone, which is offered for free, like date and time?
I may be mistaken, of course, but systems without these fundamental
features are maybe not the hottest candidates for hosting XSLT
processors anyway.
Then imagine when $government decides to change the rules for $region
next year...
System update. Due anyway. XSLT won't have to bother.
I agree that the XPath zone-conversion functions that you mention are
limited, and arguably misnamed, but they do have a use: the functions
in XPath 2.0 are enough for you to implement your own zoneinfo
database, or even to parse the Olson database file format. It's
possible to code a pure userland XSLT 2.0 implementation of zoneinfo,
but XSLT implementations which have no need for it don't have to carry
the baggage.
That's an interesting proposition. But I guess if I implemented my own
zoneinfo database (which I then would have the responsibility of keeping
in sync with the real world), I'd have to use my own timezone extension
functions as well: It would probably be difficult to convince the
built-in functions to tap into my home-grown database.
Oh, I see: I could probably use them to build my own functions which tap
into my own database. That would probably work. But then, of course, I'd
rather ask Java, or Perl, to do the timezone handling.
Michael Ludwig
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