diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/snapshotlifecycle/SnapshotLifecyclePolicyItem.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/snapshotlifecycle/SnapshotLifecyclePolicyItem.java
index c76a205f36265..62d2289cf2eee 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/snapshotlifecycle/SnapshotLifecyclePolicyItem.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/snapshotlifecycle/SnapshotLifecyclePolicyItem.java
@@ -113,7 +113,7 @@ public boolean equals(Object obj) {
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         builder.startObject(policy.getId());
         builder.field("version", version);
-        builder.field("modified_date", modifiedDate);
+        builder.timeField("modified_date_millis", "modified_date", modifiedDate);
         builder.field("policy", policy);
         if (lastSuccess != null) {
             builder.field("last_success", lastSuccess);
diff --git a/x-pack/plugin/ilm/qa/multi-node/src/test/java/org/elasticsearch/xpack/snapshotlifecycle/SnapshotLifecycleIT.java b/x-pack/plugin/ilm/qa/multi-node/src/test/java/org/elasticsearch/xpack/snapshotlifecycle/SnapshotLifecycleIT.java
index 668736b7f5327..2436a481421f0 100644
--- a/x-pack/plugin/ilm/qa/multi-node/src/test/java/org/elasticsearch/xpack/snapshotlifecycle/SnapshotLifecycleIT.java
+++ b/x-pack/plugin/ilm/qa/multi-node/src/test/java/org/elasticsearch/xpack/snapshotlifecycle/SnapshotLifecycleIT.java
@@ -93,7 +93,7 @@ public void testFullPolicySnapshot() throws Exception {
             Map<String, Object> lastSuccessObject = (Map<String, Object>) policyMetadataMap.get("last_success");
             assertNotNull(lastSuccessObject);
             Long lastSuccess = (Long) lastSuccessObject.get("time");
-            Long modifiedDate = (Long) policyMetadataMap.get("modified_date");
+            Long modifiedDate = (Long) policyMetadataMap.get("modified_date_millis");
             assertNotNull(lastSuccess);
             assertNotNull(modifiedDate);
             assertThat(lastSuccess, greaterThan(modifiedDate));
@@ -133,7 +133,7 @@ public void testPolicyFailure() throws Exception {
                 assertNotNull(lastFailureObject);
 
                 Long lastFailure = (Long) lastFailureObject.get("time");
-                Long modifiedDate = (Long) policyMetadataMap.get("modified_date");
+                Long modifiedDate = (Long) policyMetadataMap.get("modified_date_millis");
                 assertNotNull(lastFailure);
                 assertNotNull(modifiedDate);
                 assertThat(lastFailure, greaterThan(modifiedDate));