Alex Miller lives in St. Louis. He writes code for a living and currently work for Terracotta Tech on the Terracotta open-source Java clustering product. Prior to Terracotta he worked at BEA Systems and was Chief Architect at MetaMatrix. His main language for the last decade has been Java, although Alex have been paid to program in several languages over the years (C++, Python, Pascal, etc). Alex has posted 43 posts at DZone. You can read more from them at their website. View Full User Profile

JSR 310 Needs Help!

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JSR 310 is the new updated date and time library which could be added in Java 7. However, it’s currently running behind for inclusion in Java 7, according to spec lead Stephen Colebourne. Because other specs (like JDBC and NIO) will have dependencies on JSR 310, it’s important for it to get locked down early.

The great thing is that JSR 310 is an open project and YOU can help. If you can lend some hours to pull this spec over the line, we can still get it in Java 7. I for one am really tired of Date and Calendar and would love to have an updated date and time specification. Can you help?

If so, join the JSR 310 project on and get involved. Obviously, it would help if you had some background in date and time stuff but there are lots of areas needing attention. Wouldn’t it be cool to help on a core part of the JDK?

Published at DZone with permission of its author, Alex Miller. (source)

(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)


Jeroen Wenting replied on Wed, 2008/12/17 - 6:02am

it might be "cool", if I actually wanted to have my name behind that particular piece of the JDK, which in this case I don't as I consider the idea ill-conceived.

Geoffrey De Smet replied on Wed, 2008/12/17 - 6:42am

The current Calendar en Date API are a mess and some things just aren't possible.

Personally I 've been waiting for this JSR for a long time, it gets some basic stuff right. It would be shame if it didn't make it into JDK 7. Meanwhile, there's always joda time I suppose.

Ryan Developer replied on Wed, 2008/12/17 - 8:33am in response to: Jeroen Wenting

[quote=jwenting]it might be "cool", if I actually wanted to have my name behind that particular piece of the JDK, which in this case I don't as I consider the idea ill-conceived.[/quote]

Maybe you can help by elaborating on what you find wrong with the work that has been done so far. Or, do you just not like the concept of replacing Date & Calendar with a new API partly designed by the guy who wrote joda time?

cowwoc replied on Wed, 2008/12/17 - 11:38am

I don't understand Jeroen either... joda-time was a huge improvement over the JDK date/time classes. Sure it could use some simplification (a number of classes could be dropped) but on the whole I found it a very clean and satisfying API.

With respect to helping JSR 310, the most I can personally do for you is use it in my applications and provide feedback in terms of bug reporting and sanity checking for the API itself.


Paul Singh replied on Wed, 2008/12/17 - 10:36pm

Alex, I worked on big enterprise financial application, where we have to create utility date classs to support date, time functionality and methods missing in java package. This utility date class was developed base on date and time requirements from sybase database, oracle database and powerbuilder. I am open to share my knowlege and can help if required.

Jeroen Wenting replied on Thu, 2008/12/18 - 1:16am

I've used Joda time and it's a disaster. Interoperability with code that doesn't use it is far too hard to achieve (and sometimes impossible), the APIs aren't intuitive, etc. etc.

It's typical of libraries written by people with tunnelvision, an idea about how things should work in theory but no clue whatsoever about how they are going to be used in practice.

JSR310 from all I've head is basically Joda time turned into core library packages. Thanks, but no thanks.

If it were to integrate seemlessly with the existing Date and Calendar classes it might have some use, if not forget it.

cowwoc replied on Thu, 2008/12/18 - 1:54am

Seriously, I don't know where you're coming from. Converting from joda-time to Calendar/Date involves a single method call either way. For example: new DateTime(Calendar or Date) and DateTime.toCalendar(). That's just one example. You can convert pretty much any other joda-time construct back to JDK classes with ease. I've certainly never run into the kinds of problems you're reporting.


Can you provide specific  details of what doesn't work?

Mohamed El-beltagy replied on Thu, 2008/12/18 - 2:31am

First of all, I would like to thank Alex for sharing this information with us:

1- JSR 310 needs help.

2- It is open for any one who would like to share.


Second; for all those people who hates or do not like JDK Date and Time or Joda APIs; although you may/may not be correct in what you ever you say or think of saying, but that was not the intention of this post. Neither what you are saying is making any correction to the current status.

-If you have some bad experience, at least you can share it with us (exactly) so that we know that this needs to be fixed in the Date\Time APIs.

-If you have any suggestions, please let us know.

-If you have something you think is good in whatever existing APIs; please let us know.


I believe in this way, we would be able to fix or at least move forward towards a better state for the future.

Nothing is  perfect. But at least Alex is trying to get close to it.


Again, thanks Alex for your effort in this project and wishing you best of luck (for our sake at least.. ;) )

Stephen Colebourne replied on Thu, 2008/12/18 - 9:19am

Thanks for everyone offering help! The main place where info and help will be worked out will be the dev mailing list at . In particular, we're probably going to need users to ensure that the API written is suitable for the JDK and covers the main goals.

For those wondering how well JSR-310 integrates - the old Date and Calendar classes will be retrofitted with interfaces from the new API, so the integration will be pretty seamless.

 Finally, I'd also like to note the open wiki where anyone can add requirements or make comments. See the link on the JSR-310 page above.

Stephen Coleboune - co-spec lead


cowwoc replied on Thu, 2008/12/18 - 10:30am



I'd gladly give JSR-310 a try as a user, but first can you please provide an overview of where it stands now in comparison to Joda-Time? Is it suitable for daily use? What features are missing? Are there any major bugs?


Finally, if you plan on retrofitting Calendar/Date to JSR-310 instead of taking the Joda-Time approach of new DateTime(Calendar) then what are you going to do in the meantime when users try using the library under Java6 where such retrofitting has not yet happened? How are they supposed to convert there and will any sort of temporary measures you set up be removed in the final release?

cowwoc replied on Thu, 2008/12/18 - 10:50am

For what it's worth, there is a really cool video about JSR 310 here:

cowwoc replied on Thu, 2008/12/18 - 11:21am

I've added the JSR-310 mailing lists to Nabble for your convenience:

Jeroen Wenting replied on Fri, 2008/12/19 - 5:23am

if interoperability with the existing Date/Calendar system is ensured I might be interested in helping out (don't know if I'll have something useful to add of course ;) ).
As to Joda, we may have been using an old version, or the person originally using it in the project may have been doing some weird things with it.
We did have major problems with conversions though, which made me wary of the entire thing to say the least.


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