If you're using Maven, setup is easy, as DateCalc is in the Maven Central Repository.
To use the JDK Version:
<dependency>
<groupId>net.objectlab.kit</groupId>
<artifactId>datecalc-common</artifactId>
<version>1.2.0</version>
</dependency>
<dependency>
<groupId>net.objectlab.kit</groupId>
<artifactId>datecalc-jdk</artifactId>
<version>1.2.0</version>
</dependency>
To use the JODA Version (recommended):
<dependency>
<groupId>net.objectlab.kit</groupId>
<artifactId>datecalc-common</artifactId>
<version>1.2.0</version>
</dependency>
<dependency>
<groupId>net.objectlab.kit</groupId>
<artifactId>datecalc-joda</artifactId>
<version>1.2.0</version>
</dependency>
If you are not using Maven, you can download the jars here.