Thanks for your quick answers, Stephen!
> You might want to consider writing a test case that loops through time
> adding a month, seeing if the time fields stay contant (using
> different zones)
This is how I discovered the problem (in principle... in fact I did
some more complicated things where the described behaviour was a side
effect).
The "time fields" (hour, minute, second, I suppose) must change if the
time does not exist due to DST (throwing an exception would be the
alternative).
>From my point of view the month of year must *always* increase while
looping with plusMonths() (except the Dec -> Jan switch).
Looking at DateTimeField.set(long instant, int value) the time fields
can change under defined circumstances:
<javadoc>
* If setting this field would make other fields invalid, then those fields
* may be changed. For example if the current date is the 31st January, and
* the month is set to February, the day would be invalid. Instead, the day
* would be changed to the closest value - the 28th/29th February
as appropriate.
</javadoc>
May be the behaviour of DateTime.plusMonths() depends on the
documented behaviour of DateTimeField.set() (I know too few about
Joda)?
However, this is not the result an API user would expect from plusMonths().
The result from the test methods below was: in 130 of 537 timezones
the "error" occurred.
public void testPlusMonths() {
Object[] allTimeZones = DateTimeZone.getAvailableIDs().toArray();
System.out.println("OK state;Timezone Alias;Timezone name");
for (Object tz : allTimeZones) {
plusMonths((String)tz);
}
}
private void plusMonths(String tzId) {
setTimezone(tzId);
DateTime startDate;
boolean ok = true;
for (int hr = 0; hr < 24; hr++) {
try {
startDate = new DateTime(1900, 1, 1, hr, 0, 0, 0);
} catch (IllegalArgumentException e) {
// DateTime does not exist, due to timezone offset transition
continue;
}
if (plusMonthsWith(startDate) == false) {
ok = false;
break;
}
}
if (!ok) {
System.out.println("NOK;" +
DateTimeZone.getDefault().getID() + ";" + tzId);
} else {
System.out.println("OK;" +
DateTimeZone.getDefault().getID() + ";" + tzId);
}
}
private boolean plusMonthsWith(DateTime startDate) {
int latestMonth = startDate.getMonthOfYear();
int expectedMonth;
DateTime dt = startDate.toDateTime();
boolean ok = true;
for (int i=0; i<2000; i++) {
latestMonth = dt.getMonthOfYear();
dt = dt.plusMonths(1);
if (latestMonth==12) {
expectedMonth = 1;
} else {
expectedMonth = latestMonth+1;
}
//assertEquals(expectedMonth, dt.getMonthOfYear());
if (expectedMonth != dt.getMonthOfYear()) {
ok = false;
break;
}
}
return ok;
}
private void setTimezone(String id) {
DateTimeZone.setDefault(DateTimeZone.forID(id));
TimeZone.setDefault(TimeZone.getTimeZone(DateTimeZone.getDefault().getID()));
}
On 7/18/06, Stephen Colebourne <[EMAIL PROTECTED]> wrote:
> Well, its not something that I've seen before. Until I have time to
> examine the code I can't really comment further.
>
> You might want to consider writing a test case that loops through time
> adding a month, seeing if the time fields stay contant (using
> different zones)
>
> And of course, you're welcome to download the Joda-Time source and
> take a look there :-)
>
> Stephen
>
> On 18/07/06, Walter Sarka <[EMAIL PROTECTED]> wrote:
> > Some additional information under which circumstances the bug occurs
> > would be *very* helpful. E.g. if the bug occurs only for some "exotic"
> > (defineable) timezones, it would be a minor problem for me (and e.g.
> > not require a rewrite of large parts of the code using Joda).
> >
> > Just for correctness, in the sentence in my initial posting:
> > > Is this a bug or a defined behaviour (probably due to DST, since
> > > "1979-10-01T23:20:00.000-10:40" is not defined for the timezone
> > > above)?
> > it should read "1979-10-01T00:00:00.000-10:40" instead.
> >
> > Walter
> >
> >
> > On 7/18/06, Stephen Colebourne <[EMAIL PROTECTED]> wrote:
> > > 1979-09-01 + 1 month = 1979-10-01
> > > so, it looks at first glance like a bug.
> > >
> > > Stephen
> > >
> > > On 18/07/06, Walter Sarka <[EMAIL PROTECTED]> wrote:
> > > > I have a DateTime dt.
> > > > dt.toString() is "1979-09-01T00:00:00.000-10:40"
> > > > Then I add a month: dtNew = DateTime.plusMonths(1);
> > > > dtNew.toString() now is "1979-09-30T23:20:00.000-10:40".
> > > > The joda default timezone is "Pacific/Kiritimati".
> > > >
> > > > I expected dtNew to be "1979-10-01...", as the naming plusMonths()
> > > > suggests.
> > > >
> > > > Is this a bug or a defined behaviour (probably due to DST, since
> > > > "1979-10-01T23:20:00.000-10:40" is not defined for the timezone
> > > > above)?
> > > >
> > > > If it is a bug: does it only occur with "exotic" timezones or can it
> > > > happen at every DST transition?
> > > >
> > > > Can you give me some hints how to get "1979-10-01T..." (preferably
> > > > with the lowest defined time of day) for dtNew?
> > > > I suppose adding days till reaching October, but may be there is a far
> > > > better solution, since such behaviour can happen in all places where
> > > > adding or subtracting.
> > > >
> > > > Thanks, Walter.
> > > >
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