diff --git a/doc/changelog.rst b/doc/changelog.rst
index ffbe96c..9cf2870 100644
--- a/doc/changelog.rst
+++ b/doc/changelog.rst
@@ -5,9 +5,16 @@ v0.12.0
 -------
 
 API Changes
------------
+***********
+
 - mizani now requires python 3.9 and above.
 
+Bug Fixes
+*********
+
+- Fixed bug where a date with a timezone could lose the timezone. :issue:`45`.
+
+
 v0.11.4
 -------
 *2024-05-24*
diff --git a/mizani/_core/date_utils.py b/mizani/_core/date_utils.py
index 6fe0ec3..b64f1e0 100644
--- a/mizani/_core/date_utils.py
+++ b/mizani/_core/date_utils.py
@@ -291,7 +291,11 @@ def floor_day(d: datetime) -> datetime:
     """
     Round down to the start of the day
     """
-    return d.min.replace(d.year, d.month, d.day) if has_time(d) else d
+    return (
+        d.min.replace(d.year, d.month, d.day, tzinfo=d.tzinfo)
+        if has_time(d)
+        else d
+    )
 
 
 def ceil_day(d: datetime) -> datetime: