diff --git a/src/corelibs/string_handling/timestamp_strings.py b/src/corelibs/string_handling/timestamp_strings.py
index b0581c7..eb3d215 100644
--- a/src/corelibs/string_handling/timestamp_strings.py
+++ b/src/corelibs/string_handling/timestamp_strings.py
@@ -11,11 +11,11 @@ class TimestampStrings:
     set default time stamps
     """
 
-    time_zone: str = 'Asia/Tokyo'
+    TIME_ZONE: str = 'Asia/Tokyo'
 
     def __init__(self, time_zone: str | None = None):
         self.timestamp_now = datetime.now()
-        self.time_zone = time_zone if time_zone is not None else self.time_zone
+        self.time_zone = time_zone if time_zone is not None else self.TIME_ZONE
         try:
             self.timestamp_now_tz = datetime.now(ZoneInfo(self.time_zone))
         except ZoneInfoNotFoundError as e:
diff --git a/tests/unit/string_handling/test_timestamp_strings.py b/tests/unit/string_handling/test_timestamp_strings.py
index 03677ca..433f11d 100644
--- a/tests/unit/string_handling/test_timestamp_strings.py
+++ b/tests/unit/string_handling/test_timestamp_strings.py
@@ -82,7 +82,7 @@ class TestTimestampStrings:
 
     def test_class_default_timezone(self):
         """Test that class default timezone is correctly set"""
-        assert TimestampStrings.time_zone == 'Asia/Tokyo'
+        assert TimestampStrings.TIME_ZONE == 'Asia/Tokyo'
 
     def test_none_timezone_uses_default(self):
         """Test that passing None for timezone uses class default"""