Try using env vars for the date?

.forgejo/workflows/build.yml

@@ -24,6 +24,10 @@ jobs:
         uses: actions/checkout@v4
       - name: buildx-base
         uses: https://github.com/docker/setup-buildx-action@v3
+      - name: setup formatted date
+        run:
+          - echo $( date -I )
+          - echo FMT_DATE=$( date -I ) >> $GITHUB_ENV
       - name: Build and push
         uses: https://github.com/docker/build-push-action@v6
         with:
@@ -35,4 +39,4 @@ jobs:
           build-args: |
             PG_MAJOR_VERSION=${{ matrix.PG_MAJOR_VERSION }}
             DEB_RELEASE=${{ matrix.DEB_RELEASE }}
-            FMT_DATE=${{ date 'YYYY-MM-DD' }}
+            FMT_DATE=${{ env.FMT_DATE }}