Try using the docker meta setup?

.forgejo/workflows/build.yml

@@ -10,6 +10,14 @@ jobs:
       - DEB_RELEASE:
         - bookworm
     steps:
+      - name: Setup metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: gitea.simcop2387.info/simcop2387/pg-container-base
+          tags:
+            type=raw,value={{ env.PG_MAJOR_VERSION }}-{{ env.DEB_RELEASE }}
+            type=raw,value={{ env.PG_MAJOR_VERSION }}-{{ env.DEB_RELEASE }}-{{ date 'YYYY-MM-DD' }}
       - name: checkout
         uses: actions/checkout@v4
       - name: buildx-base
@@ -20,6 +28,6 @@ jobs:
         uses: https://github.com/docker/build-push-action@v6
         with:
           push: true
-          tags: "gitea.simcop2387.info/simcop2387/pg-container-base:${ PG_MAJOR_VERSION }-${ DEB_RELEASE },gitea.simcop2387.info/simcop2387/pg-container-base:${ PG_MAJOR_VERSION }-${ DEB_RELEASE }-${ FMT_DATE }"
+          tags: {{ steps.meta.outputs.tags }} 
           context: base/
           dockerfile: base/Dockerfile