diff --git a/flagsmith/mappers.py b/flagsmith/mappers.py
index 7564a89..5e6156d 100644
--- a/flagsmith/mappers.py
+++ b/flagsmith/mappers.py
@@ -28,6 +28,7 @@
     StreamEvent,
     TraitConfig,
 )
+from flagsmith.utils.datetime import fromisoformat
 
 OverrideKey = typing.Tuple[
     int,
@@ -69,9 +70,7 @@ def map_sse_event_to_stream_event(event: sseclient.Event) -> StreamEvent:
 def map_environment_document_to_environment_updated_at(
     environment_document: dict[str, typing.Any],
 ) -> datetime:
-    if (
-        updated_at := datetime.fromisoformat(environment_document["updated_at"])
-    ).tzinfo is None:
+    if (updated_at := fromisoformat(environment_document["updated_at"])).tzinfo is None:
         return updated_at.replace(tzinfo=timezone.utc)
     return updated_at.astimezone(tz=timezone.utc)
 
diff --git a/flagsmith/utils/datetime.py b/flagsmith/utils/datetime.py
new file mode 100644
index 0000000..4df38fb
--- /dev/null
+++ b/flagsmith/utils/datetime.py
@@ -0,0 +1,10 @@
+import sys
+
+if sys.version_info >= (3, 11):
+    from datetime import datetime
+
+    fromisoformat = datetime.fromisoformat
+else:
+    import iso8601
+
+    fromisoformat = iso8601.parse_date
diff --git a/poetry.lock b/poetry.lock
index 4d9f539..8fa5407 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -341,6 +341,19 @@ files = [
     {file = "iregexp_check-0.1.4.tar.gz", hash = "sha256:a98e77dd2d9fc91db04f8d9f295f3d69e402813bac5413f22e5866958a902bc1"},
 ]
 
+[[package]]
+name = "iso8601"
+version = "2.1.0"
+description = "Simple module to parse ISO 8601 dates"
+optional = false
+python-versions = ">=3.7,<4.0"
+groups = ["main"]
+markers = "python_version < \"3.11\""
+files = [
+    {file = "iso8601-2.1.0-py3-none-any.whl", hash = "sha256:aac4145c4dcb66ad8b648a02830f5e2ff6c24af20f4f482689be402db2429242"},
+    {file = "iso8601-2.1.0.tar.gz", hash = "sha256:6b1d3829ee8921c4301998c909f7829fa9ed3cbdac0d3b16af2d743aed1ba8df"},
+]
+
 [[package]]
 name = "jsonpath-rfc9535"
 version = "0.1.6"
@@ -947,4 +960,4 @@ test = ["covdefaults (>=2.3)", "coverage (>=7.2.7)", "coverage-enable-subprocess
 [metadata]
 lock-version = "2.1"
 python-versions = ">=3.9,<4"
-content-hash = "cfe10e9fdb3ea780c9d8fae0f9cf8b92b3a37356be13633f655d910f71e0035e"
+content-hash = "22ba0b94f5228702454729e8f3962ecb316d1caf4d69f47df478c04735c67ab2"
diff --git a/pyproject.toml b/pyproject.toml
index 95ca3fe..f773994 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -11,6 +11,7 @@ packages = [{ include = "flagsmith" }]
 
 [tool.poetry.dependencies]
 flagsmith-flag-engine = "^10.0.0"
+iso8601 = { version = "^2.1.0", python = "<3.11" }
 python = ">=3.9,<4"
 requests = "^2.32.3"
 requests-futures = "^1.0.1"
diff --git a/tests/data/environment.json b/tests/data/environment.json
index ea63981..0075f01 100644
--- a/tests/data/environment.json
+++ b/tests/data/environment.json
@@ -54,13 +54,13 @@
             "enabled": true
         }
     ],
-    "updated_at": "2023-07-14 16:12:00.000000",
+    "updated_at": "2023-07-14T16:12:00.000000Z",
     "identity_overrides": [
         {
             "identifier": "overridden-id",
             "identity_uuid": "0f21cde8-63c5-4e50-baca-87897fa6cd01",
             "created_date": "2019-08-27T14:53:45.698555Z",
-            "updated_at": "2023-07-14 16:12:00.000000",
+            "updated_at": "2023-07-14T16:12:00.000000Z",
             "environment_api_key": "B62qaMZNwfiqT76p38ggrQ",
             "identity_features": [
                 {