Use isotime instead of unix timestamp
diff --git a/centos-7/template.json b/centos-7/template.json
index 6c0c04f..50f1b53 100644
--- a/centos-7/template.json
+++ b/centos-7/template.json
@@ -61,7 +61,7 @@
     {
       "type": "vagrant",
       "keep_input_artifact": true,
-      "output": "images/{{ user `distro` }}-{{.Provider}}-{{ timestamp }}.box",
+      "output": "images/{{ user `distro` }}-{{.Provider}}-{{ isotime \"200601020304\" }}.box",
       "except": [ "docker" ]
     },
     {
@@ -72,7 +72,7 @@
     },
     {
       "type": "docker-save",
-      "path": "images/{{ user `distro` }}-docker-{{ timestamp }}.tar",
+      "path": "images/{{ user `distro` }}-docker-{{ isotime \"200601020304\" }}.tar",
       "only": ["docker"]
     }
   ],
@@ -84,7 +84,7 @@
       ],
       "boot_wait": "10s",
       "disk_size": 5020,
-      "output_directory": "images/{{ user `distro` }}-vbox-{{ timestamp  }}",
+      "output_directory": "images/{{ user `distro` }}-vbox-{{ isotime \"200601020304\"  }}",
       "guest_os_type": "RedHat_64",
       "http_directory": "http",
       "iso_checksum": "88c0437f0a14c6e2c94426df9d43cd67",
@@ -107,8 +107,8 @@
       "qemuargs": [
         [ "-m", "1024M" ]
       ],
-      "vm_name": "{{ user `distro` }}-{{ timestamp  }}",
-      "output_directory": "images/{{ user `distro` }}-qemu-{{ timestamp  }}",
+      "vm_name": "{{ user `distro` }}-{{ isotime \"200601020304\"  }}",
+      "output_directory": "images/{{ user `distro` }}-qemu-{{ isotime \"200601020304\"  }}",
       "format": "qcow2",
       "accelerator": "kvm",
       "disk_size": "{{ user `disk_size`}}",
@@ -138,7 +138,7 @@
       ],
       "boot_wait": "10s",
       "disk_size": 40520,
-      "output_directory": "images/{{ user `distro` }}-vmware-{{ timestamp  }}",
+      "output_directory": "images/{{ user `distro` }}-vmware-{{ isotime \"200601020304\"  }}",
       "guest_os_type": "centos-64",
       "http_directory": "http",
       "iso_checksum": "154ba47b7a37e52e0100310c3aeb8f9d9daf4806",