diff --git a/agent/tools/scheduler/time_utils.py b/agent/tools/scheduler/time_utils.py
index 0b27be7c..7f1c7bdc 100644
--- a/agent/tools/scheduler/time_utils.py
+++ b/agent/tools/scheduler/time_utils.py
@@ -7,7 +7,16 @@ naive local-time behaviour so existing stored tasks are not reinterpreted.
 """
 from croniter import croniter
 from datetime import datetime, timedelta, timezone
-from zoneinfo import ZoneInfo
+
+# zoneinfo joined the standard library in Python 3.9. Without it, only named
+# IANA timezones are unavailable; legacy naive-local tasks keep working.
+try:
+    from zoneinfo import ZoneInfo
+except ImportError:
+    try:
+        from backports.zoneinfo import ZoneInfo
+    except ImportError:
+        ZoneInfo = None
 
 UTC = timezone.utc
 
@@ -38,6 +47,10 @@ def resolve_timezone(name=None):
         return datetime.now().astimezone().tzinfo
     if not isinstance(name, str) or not name.strip():
         raise ValueError("timezone must be a non-empty IANA name")
+    if ZoneInfo is None:
+        raise ValueError(
+            "IANA timezones require Python 3.9+ or the backports.zoneinfo package"
+        )
     return ZoneInfo(name.strip())
 
 
diff --git a/desktop/build/requirements-desktop.txt b/desktop/build/requirements-desktop.txt
index 14826d45..d6c9907e 100644
--- a/desktop/build/requirements-desktop.txt
+++ b/desktop/build/requirements-desktop.txt
@@ -28,6 +28,9 @@ Pillow
 python-dotenv>=1.0.0
 PyYAML>=6.0
 croniter>=2.0.0
+# zoneinfo is stdlib from 3.9 (the Win7 build runs 3.8); Windows has no system tz database
+backports.zoneinfo; python_version < "3.9"
+tzdata; sys_platform == "win32"
 click>=8.0
 qrcode
 json-repair
diff --git a/requirements.txt b/requirements.txt
index ec5af851..40ecfe1a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -11,6 +11,9 @@ Pillow
 python-dotenv>=1.0.0
 PyYAML>=6.0
 croniter>=2.0.0
+# zoneinfo is stdlib from 3.9; Windows has no system tz database
+backports.zoneinfo; python_version < "3.9"
+tzdata; sys_platform == "win32"
 click>=8.0
 qrcode
 json-repair