diff --git a/Jenkinsfile b/Jenkinsfile
index f483e0b..d93ea0e 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -64,8 +64,9 @@ pipeline {
 
                     try {
                         // Staleness threshold: 90 days ago as unix epoch
+                        // GNU date (Linux): -d '90 days ago'; BSD date (macOS): -v-90d
                         def threeMonthsAgoStr = sh(
-                            script: "date -d '90 days ago' +%s",
+                            script: "date -d '90 days ago' +%s 2>/dev/null || date -v-90d +%s",
                             returnStdout: true
                         ).trim()
                         if (!threeMonthsAgoStr.isLong()) {
@@ -91,7 +92,7 @@ pipeline {
                             if (branch.startsWith('pr/')) continue
                             def commitEpochStr = withEnv(["BRANCH_TO_CHECK=${branch}"]) {
                                 sh(
-                                    script: "git -C '${tmpBareClone}' log -1 --format='%ct' -- \"\$BRANCH_TO_CHECK\"",
+                                    script: "git -C '${tmpBareClone}' log -1 --format='%ct' \"refs/heads/\$BRANCH_TO_CHECK\"",
                                     returnStdout: true
                                 ).trim()
                             }
@@ -147,10 +148,19 @@ pipeline {
                             "SKARA_REPO_ARG=${params.SKARA_REPO}",
                             "MIRROR_REPO_ARG=${mirrorRepoArg}"
                         ]) {
-                            sh '''
-                                git --version
-                                bash ./skaraMirror.sh "$SKARA_REPO_ARG" "$MIRROR_REPO_ARG"
-                            '''
+                            def mirrorSteps = {
+                                sh '''
+                                    git --version
+                                    bash ./skaraMirror.sh "$SKARA_REPO_ARG" "$MIRROR_REPO_ARG"
+                                '''
+                            }
+                            if (params.SSH_CREDENTIAL_ID?.trim()) {
+                                sshagent(credentials: [params.SSH_CREDENTIAL_ID]) {
+                                    mirrorSteps()
+                                }
+                            } else {
+                                mirrorSteps()
+                            }
                         }
                     }
                 }