1. explicit -DforceContextQualifier command line parameter
2. forceContextQualifier from ${project.baseDir}/build.properties
3. a time stamp in the form YYYYMMDDHHMM (ie 200605121600)

The generated qualifier is assigned to buildQualifier project property. Unqualified project version is assigned to unqualifiedVersion project property. Unqualified version is calculated based on ${project.version} and can be used for any Tycho project (eclipse-update-site, eclipse-application, etc) and regular maven project. Different projects can use different formats to expand the timestamp, however (highly not recommended but possible).

Starting with version 0.16, it is now possible to use custom build timestamp generation logic. The primary usecase is to generate build version qualifier based on the timestamp of the last project commit. Here is example pom.xml snippet that enables custom timestamp generation logic

     ...
     <plugin>
        <groupId>org.eclipse.tycho</groupId>
        <artifactId>tycho-packaging-plugin</artifactId>
        <version>${tycho-version}</version>
        <dependencies>
          <dependency>
            <groupId>timestamp-provider-groupid</groupId>
            <artifactId>timestamp-provider-artifactid</artifactId>
            <version>timestamp-provider-version</version>
          </dependency>
        </dependencies>
        <configuration>
          <timestampProvider>custom</timestampProvider>
        </configuration>
     </plugin>
     ...