diff --git a/CHANGELOG.md b/CHANGELOG.md
index e66e2b97..2e161e4f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Fixed
 
+- Fixed datetime filtering for .0Z milliseconds to preserve precision in apply_filter_datetime, ensuring only items exactly within the specified range are returned. [#535](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/535)
+
 ### Removed
 
 ### Updated
diff --git a/stac_fastapi/core/stac_fastapi/core/datetime_utils.py b/stac_fastapi/core/stac_fastapi/core/datetime_utils.py
index 587f2d0b..38a37036 100644
--- a/stac_fastapi/core/stac_fastapi/core/datetime_utils.py
+++ b/stac_fastapi/core/stac_fastapi/core/datetime_utils.py
@@ -32,7 +32,10 @@ def normalize(dt):
                 dt_utc = MIN_DATE_NANOS
             if dt_utc > MAX_DATE_NANOS:
                 dt_utc = MAX_DATE_NANOS
-            return dt_utc.isoformat(timespec="auto").replace("+00:00", "Z")
+            dt_normalized = dt_utc.isoformat(timespec="auto").replace("+00:00", "Z")
+            if "." not in dt_normalized:
+                dt_normalized = dt_normalized.replace("Z", ".0Z")
+            return dt_normalized
 
         if not isinstance(date_str, str):
             return f"{MIN_DATE_NANOS.isoformat(timespec='auto').replace('+00:00','Z')}/{MAX_DATE_NANOS.isoformat(timespec='auto').replace('+00:00','Z')}"