[tz] Joda-Time, Time4J, and Java SE 8

Stephen Colebourne scolebourne at joda.org
Fri Jul 8 11:34:34 UTC 2016

For many years, Joda-Time has been the de facto default library for
date and time in Java. In the last few years two things have happened.
1) Time4J came out (no idea how widely used it is)
2) Java 8 was enhanced with a new date/time API "inspired by"
Joda-Time (because I wrote both)

The Java 8 code is also supplemented by ThreeTen-Extra (which includes
leap second support).

The Java 8 code has been backported to Java 6 and 7 (but this is only
for specialised use cases).

Joda-Time will over time be less and less used as people migrate to
Java 8, supported by ThreeTen-Extra if needed.

I would recommend keeping the Time4J line in tzlink separate from the
Joda-Time/Java 8 line, as while Joda-Time and Java 8 have a lot in
common, Time4J doesn't have any history in common at all. It also
allows you to simplify the license part, which is complex as written.

<li><a href="https://github.com/MenoData/Time4J/">Time4J &ndash;
Advanced date, time and interval library for Java</a> contains a class
<code>net.time4j.tool.TimezoneRepositoryCompiler</code> that compiles
<code><abbr>tz</abbr></code> source into a binary format. Time4J is
available under the <a
href="http://www.gnu.org/copyleft/lesser.html"><abbr>GNU</abbr> Lesser
General Public License (<abbr title="Lesser General Public

<li><a href="http://www.joda.org/joda-time/">Joda-Time &ndash; Java
date and time <abbr>API</abbr></a> contains a class
<code><abbr>tz</abbr></code> source into a binary format. Joda-Time is
available under the <a
href="http://www.apache.org/licenses/LICENSE-2.0">Apache License
v2</a>. From Java 8 onwards, users are recommended to migrate to the
new built-in <a
SE 8 <code>java.time</code> API</a> API that was inspired by
Joda-Time, supplemented by <a
href="http://www.threeten.org/threeten-extra/">ThreeTen-Extra</a> if


On 8 July 2016 at 11:45, Paul Eggert <eggert at cs.ucla.edu> wrote:
> On 07/08/2016 06:23 AM, Meno Hochschild wrote:
>> it is not quite correct to say that Joda-Times "functionality is a
>> standard part of Java 8". It has rather inspired the development of
>> java.time-package in Java-8.
> Thanks for the correction. Sorry, I don't know Joda-Time vs Java SE 8 vs
> Time4J well.
> I'm trying to future-proof tz-link.htm. As I understand it from the
> Joda-Time web page, Joda-Time-using apps are expected to migrate to the Java
> SE 8 API, so future readers of tz-link.htm will mostly be using the Java
> API, with more-specialized uses (leap seconds? sorry, don't know the
> details) possibly using Time4J, and Joda-Time being a historical footnote.
> I installed the attached further patch into the experimental tz version on
> GitHub; I hope it addresses this point well enough. I'll CC: Stephen
> Colebourne to give him a heads-up, as I do want tz-link.htm to be accurate.

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