Re: NSTimestamp problem
Re: NSTimestamp problem
- Subject: Re: NSTimestamp problem
- From: Bob Stuart <email@hidden>
- Date: Mon, 18 Dec 2006 23:35:03 -0500
Title: Re: NSTimestamp problem
I notice the sun tool says:
The java.vendor
property value must be "Sun Microsystems Inc.".
so I bet it won't work for Apple JVMs. It didn't appear that
Apple had a JVM release that met the dates shown on the sun page.
Maybe we are stuck?
At 11:15 PM -0500 12/18/06, Ken Anderson wrote:
Jim,
Do you know which, if any, Apple updates
have the required file?
Thanks,
Ken
On Dec 18, 2006, at 10:43 PM, James Stead
wrote:
Hi,
I've been working on this problem at a
client recently. Pre-1.4 jvm's kept the timezone data as a structure
inside a java class, and 1.4+ jvm's keep the data in the Olson
TimeZoneInfo database http://www.twinsun.com/tz/tz-link.htm. To patch the pre-1.4s the
class file must be replaced. To patch the post 1.4s the database (a
filesystem based structure) must be replaced.
Either may be handled by updating your
jdk to a version that has the update. Alternatively you can patch
*only* the date functionality. To do so for post 1.4, try the
tzupdater by Sun http://java.sun.com/javase/tzupdater_README.html. Prior jdk's
require a modification to the class file. For example, to patch a
1.1.8 version used by WO 4.5 it is possible to decompile the class in
classes.zip, fix the dst start/end dates, and recompile.
Thanks.
Jim
On Dec 18, 2006, at 10:10 PM, Ken
Anderson wrote:
Chuck,
The distinction here is that DST is
actually starting at a new time in 2007 (a few weeks earlier than it
used to) and there's a lot of fuss about what JVM's are handling it
correctly.
Ken
On Dec 18, 2006, at 10:05 PM, Chuck Hill
wrote:
On Dec 18, 2006, at 6:45 PM, Jerry W.
Walker wrote:
Hi, Dan,
You're dealing with a Daylight Savings
Time problem.
Yes, the notorious One Hour
Shift.
I haven't tried to keep up with Java's
calendar routines over the last few months, but if you go to the page
on the US Naval Observatory web site that describes clock changes
at:
http://aa.usno.navy.mil/faq/docs/daylight_time.html
...the first paragraph says:
Currently,
daylight time begins in the United States
on the first
Sunday in April and ends on the last
Sunday in
October. On the first Sunday in April,
clocks are set
ahead one hour at 2:00 a.m. local
standard time,
which becomes 3:00 a.m. local
daylight time.
On the last Sunday in October, clocks
are set back one
hour at 2:00 a.m. local daylight
time, which
becomes 1:00 a.m. local standard time.
These dates were
recently modified with the
passage of the
Energy Policy Act of 2005, Pub. L.
no. 109-58, 119
Stat 594 (2005). Starting in
March 2007,
daylight time in the United States
will begin on
the second Sunday in March and end
on the first
Sunday in November.
...and therein lies your
problem.
As for a workaround, I'm not sure what to
suggest. However, I thought that the later JVMs had adapted to the
change in law.
I think that is exactly the problem.
We are not in DST now, but late March will be. Java is very
"accurate" WRT time and does not handle it as we would in
day to day life. 9AM March 21 is not exactly N x 24 hours away,
it is N x 24 +/- 1 depending on which way you are crossing the
DST boundary. If you have dates at midnight, even the date will
change! Much fin ensues. If you don't need the time,
setting it to noon will avoid the date shift. That is of no use
to you. You can use different formatters (with the time zone set
differently) for dates in and out of DST. You could also store
the date (at noon) in one field and the in another.
Java. Dates. If there is a
hell on earth for developers, it is this.
Chuck
On Dec 18, 2006, at 8:31 PM, Dan Faber
wrote:
Hi everyone:
I have just run into an apparent
NSTimestamp problem. I have a scheduling program, and it has been
working well. Recently we tried to schedule an appt for March, and the
NSTimestamp is giving us back a time that is one hour earlier than the
time that is designated. This occurs between March 11 and March 31,
2007, a 3 week period. The problem does not seem to occur for dates
before that period or afterwards. It does not appear to be an
NSTimestampFormatter problem, as it exists with or without using the
formatter.
The time is correct in the database after
a save, but it immediately gets displayed an hour early. The problem
occurs with two different versions of the mysql-connector (including
the most recent). It occurs on two different machines, both running
OSX version 10.4.8.
Converting the date to
java.util.GregorianCalendar appears to produce the correct result for
java.util.GregorianCalendar.HOUR_OF_DAY.
So far I have not seen anything on the
list about this. Anyone have any ideas what's up?
Dan Faber
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