diff --git a/homeassistant/helpers/template.py b/homeassistant/helpers/template.py
index 4c6888cbf2f..ca2828c4402 100644
--- a/homeassistant/helpers/template.py
+++ b/homeassistant/helpers/template.py
@@ -1462,9 +1462,7 @@ def timestamp_custom(value, date_format=DATE_STR_FORMAT, local=True, default=_SE
 def timestamp_local(value, default=_SENTINEL):
     """Filter to convert given timestamp to local date/time."""
     try:
-        return dt_util.as_local(dt_util.utc_from_timestamp(value)).strftime(
-            DATE_STR_FORMAT
-        )
+        return dt_util.as_local(dt_util.utc_from_timestamp(value)).isoformat()
     except (ValueError, TypeError):
         # If timestamp can't be converted
         if default is _SENTINEL:
@@ -1476,7 +1474,7 @@ def timestamp_local(value, default=_SENTINEL):
 def timestamp_utc(value, default=_SENTINEL):
     """Filter to convert given timestamp to UTC date/time."""
     try:
-        return dt_util.utc_from_timestamp(value).strftime(DATE_STR_FORMAT)
+        return dt_util.utc_from_timestamp(value).isoformat()
     except (ValueError, TypeError):
         # If timestamp can't be converted
         if default is _SENTINEL:
diff --git a/tests/helpers/test_template.py b/tests/helpers/test_template.py
index f1dc740a068..1a8bf8e526b 100644
--- a/tests/helpers/test_template.py
+++ b/tests/helpers/test_template.py
@@ -692,7 +692,7 @@ def test_timestamp_custom(hass):
 
 def test_timestamp_local(hass):
     """Test the timestamps to local filter."""
-    tests = {None: None, 1469119144: "2016-07-21 16:39:04"}
+    tests = {None: None, 1469119144: "2016-07-21T16:39:04+00:00"}
 
     for inp, out in tests.items():
         assert (
@@ -859,8 +859,8 @@ def test_timestamp_utc(hass):
     now = dt_util.utcnow()
     tests = {
         None: None,
-        1469119144: "2016-07-21 16:39:04",
-        dt_util.as_timestamp(now): now.strftime("%Y-%m-%d %H:%M:%S"),
+        1469119144: "2016-07-21T16:39:04+00:00",
+        dt_util.as_timestamp(now): now.isoformat(),
     }
 
     for inp, out in tests.items():