diff --git a/book/pom.xml b/book/pom.xml
index c10954f..cb02840 100644
--- a/book/pom.xml
+++ b/book/pom.xml
@@ -33,6 +33,8 @@ along with semanticcms-file-bom.  If not, see <https://www.gnu.org/licenses/>.
   <packaging>jar</packaging>
 
   <properties>
+    <!-- Must be set to ${git.commit.time} for snapshots or ISO 8601 timestamp for releases. -->
+    <project.build.outputTimestamp>${git.commit.time}</project.build.outputTimestamp>
     <module.name>com.semanticcms.file.bom.book</module.name>
     <!-- These values are copied from the project being documented -->
     <documented.artifactId>semanticcms-file-bom</documented.artifactId>
diff --git a/pom.xml b/pom.xml
index bedbb41..b6261f0 100644
--- a/pom.xml
+++ b/pom.xml
@@ -32,6 +32,11 @@ along with semanticcms-file-bom.  If not, see <https://www.gnu.org/licenses/>.
   <groupId>com.semanticcms</groupId><artifactId>semanticcms-file-bom</artifactId><version>2.0.0-SNAPSHOT</version>
   <packaging>pom</packaging>
 
+  <properties>
+    <!-- Must be set to ${git.commit.time} for snapshots or ISO 8601 timestamp for releases. -->
+    <project.build.outputTimestamp>${git.commit.time}</project.build.outputTimestamp>
+  </properties>
+
   <name>SemanticCMS File BOM</name>
   <url>https://semanticcms.com/file/bom/</url>
   <description>Bill of Materials (BOM) for SemanticCMS File features.</description>