Re: Date-Only NSTimestamps
Re: Date-Only NSTimestamps
- Subject: Re: Date-Only NSTimestamps
- From: Chuck Hill <email@hidden>
- Date: Wed, 2 Jan 2008 20:20:18 -0800
On Jan 2, 2008, at 1:51 PM, Simon McLean wrote:
It should be possible to normalize it at 12:00 GMT instead of the
default time zone. I need to try that out.
IIRC all timestamps are stored at GMT.
Yes.
So if you do this on an object:
setCreateTimeStamp(new NSTimestamp());
at 01 Jan 08 00:01 on a server that is at BST then it get's stored
as 31 Dec 08 23:01 GMT
Yes, it is the conversion to / from the local time zone where things
get odd.
So if you then query using a qualifier to find things created after
01 Jan 08 00:00 at GMT, you miss this object.
The qualifier values are also subject to this same conversion. It is
a problem when the value is saved during DST and then queried when
DST is not in effect (or vice versa).
Working at GMT is definitely one way of easing the pain, but i
think everything has to be at GMT for it to work - which i guess is
most easily accomplished by setting the default time time zone to
GMT. But then you get a whole new world of pain because you have to
convert timestamps on the fly for presenting to your users!
I am not convinced that this will solve anything. That is what WO is
doing already. The problem is that we really want less accuracy than
Java provides. we want to ignore things like DST. I think the only
thing that will work is to format the dates to / from GMT. That is
when the user types in 2PM parse it as if it is 2PM GMT not 2PM in
the local time zone. I think this will work, but not if your app is
used by people in more than one time zone. If it is used in more
than one time zone, well, its just hard.
I work in the travel industry and hence date/time stuff is pretty
interesting (eg flights taking off in one time zone and landing 2
days later in another timezone, or presenting a hotel cancellation
policy stored in one timezone to a user in another timezone so they
know when they need to cancel it by locally).
That is a hell that I would not wish on myself.
Chuck
--
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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