diff --git a/src/apify_client/_http_client.py b/src/apify_client/_http_client.py
index cf166059..5f3c76d2 100644
--- a/src/apify_client/_http_client.py
+++ b/src/apify_client/_http_client.py
@@ -80,8 +80,10 @@ def _parse_params(params: dict | None) -> dict | None:
             elif isinstance(value, datetime):
                 utc_aware_dt = value.astimezone(timezone.utc)
 
+                iso_str = utc_aware_dt.isoformat(timespec='milliseconds')
+
                 # Convert to ISO 8601 string in Zulu format
-                zulu_date_str = utc_aware_dt.strftime('%Y-%m-%dT%H:%M:%SZ')
+                zulu_date_str = iso_str.replace('+00:00', 'Z')
 
                 parsed_params[key] = zulu_date_str
             elif value is not None: