low-level utilities in DateTimeZone to find the next transition. That
> I've never used Joda time before now, but I know of it's reputation
> and it seems like a natural fit for the problem I'm trying to solve.
>
> I'm working on an application that sends notifications to users'
> iPhones. These notifications can be generated at any time of day, and
> I have a requirement to support the concept of a "Do Not Disturb"
> (DND) interval for each user. The reasoning is that some users may
> wish to avoid being bothered with notifications during certain hours
> of the day (such as the overnight hours). If the application needs to
> send a notification to a user it should do so only if the current time
> falls outside of the user's specified DND interval.
>
> I plan on storing the following information in each user's profile:
>
> - User's time zone
> - DND begin hour of day & minute of hour
> - DND end hour of day & minute of hour
>
> With this information a user can effectively tell the system, for
> example, "I'm in the US/Pacific time zone, and I do not wish to be
> notified between 00:00 and 06:00". In this case I create the following
> Joda objects using information from the user's profile:
>
> LocalTime dndBeginTime = new LocalTime(0, 0);
> LocalTime dndEndTime = new LocalTime(6, 0);
> DateTimeZone userTimeZone = DateTimeZone.forID("US/
> Pacific");
>
> Now I need to figure out where the current time falls in relation to
> the DND interval specified by the user, so I use this code:
>
> // First create an Interval with the user's time zone and
> // bounded by the begin & end times in the user's profile
> DateTime dndBegin = dndBeginTime.toDateTimeToday(userTimeZone);
> DateTime dndEnd = dndEndTime.toDateTimeToday(userTimeZone);
> Interval dndInterval = new Interval(dndBegin, dndEnd);
>
> if (dndInterval.containsNow()) {
> // Inside the DND interval- do not send the notification
> }
> else {
> // Outside the DND interval- send the notification
> }
>
> This code seemed to work well until I hit upon a problem caused by
> Daylight Savings Time. Suppose the user specifies a time that is
> within the 02:00 hour, for example:
>
> LocalTime dndBeginTime = new LocalTime(2, 30);
>
> In this case my code will fail on the following line during the
> transition from Standard Time to Daylight Savings Time:
>
> DateTime dndBegin = dndBeginTime.toDateTimeToday(userTimeZone);
>
> I get the following exception (I used DateTimeUtils to set the date
> for testing- great feature BTW):
>
> org.joda.time.IllegalFieldValueException: Value 2 for hourOfDay is
> not supported:
> Illegal instant due to time zone offset transition:
> 2010-03-14T02:30:00.000 (America/Los_Angeles)
>
> I understand why this is happening: there is no 02:30 instant on March
> 14, 2010. Time jumps from 01:59 directly to 03:00. However, I'd like
> to deal with this more gracefully. Logically, the user still has a DND
> internal- it's just been shortened by 30 minutes.
>
> Does anyone have any suggestions for dealing with this? I suspect
> there may be a better way somewhere in the API, but I'm not seeing it
> right now.
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