diff --git a/pandas/_libs/tslibs/conversion.pyx b/pandas/_libs/tslibs/conversion.pyx
index cbb27bf8e9917..b0bad119d6a46 100644
--- a/pandas/_libs/tslibs/conversion.pyx
+++ b/pandas/_libs/tslibs/conversion.pyx
@@ -788,7 +788,16 @@ cpdef ndarray[int64_t] normalize_i8_timestamps(const int64_t[:] stamps, tzinfo t
         npy_datetimestruct dts
         int64_t delta, local_val
 
-    if is_tzlocal(tz):
+    if tz is None or is_utc(tz):
+        with nogil:
+            for i in range(n):
+                if stamps[i] == NPY_NAT:
+                    result[i] = NPY_NAT
+                    continue
+                local_val = stamps[i]
+                dt64_to_dtstruct(local_val, &dts)
+                result[i] = _normalized_stamp(&dts)
+    elif is_tzlocal(tz):
         for i in range(n):
             if stamps[i] == NPY_NAT:
                 result[i] = NPY_NAT
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index a7c4b44cf95f8..fad87f9f910cb 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -1451,13 +1451,8 @@ default 'raise'
             ndarray[int64_t] normalized
             tzinfo own_tz = self.tzinfo  # could be None
 
-        if own_tz is None or is_utc(own_tz):
-            DAY_NS = ccalendar.DAY_NANOS
-            normalized_value = self.value - (self.value % DAY_NS)
-            return Timestamp(normalized_value).tz_localize(own_tz)
-
         normalized = normalize_i8_timestamps(
-            np.array([self.value], dtype='i8'), tz=own_tz)
+            np.array([self.value], dtype="i8"), tz=own_tz)
         return Timestamp(normalized[0]).tz_localize(own_tz)
 
 
diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py
index 4e31477571a5f..bade1c031d556 100644
--- a/pandas/core/arrays/datetimes.py
+++ b/pandas/core/arrays/datetimes.py
@@ -9,15 +9,14 @@
 from pandas._libs.tslibs import (
     NaT,
     Timestamp,
-    ccalendar,
     conversion,
     fields,
+    frequencies as libfrequencies,
     iNaT,
     resolution as libresolution,
     timezones,
     tzconversion,
 )
-import pandas._libs.tslibs.frequencies as libfrequencies
 from pandas.errors import PerformanceWarning
 
 from pandas.core.dtypes.common import (
@@ -1036,14 +1035,7 @@ def normalize(self):
                        '2014-08-01 00:00:00+05:30'],
                        dtype='datetime64[ns, Asia/Calcutta]', freq=None)
         """
-        if self.tz is None or timezones.is_utc(self.tz):
-            not_null = ~self.isna()
-            DAY_NS = ccalendar.DAY_SECONDS * 1_000_000_000
-            new_values = self.asi8.copy()
-            adjustment = new_values[not_null] % DAY_NS
-            new_values[not_null] = new_values[not_null] - adjustment
-        else:
-            new_values = conversion.normalize_i8_timestamps(self.asi8, self.tz)
+        new_values = conversion.normalize_i8_timestamps(self.asi8, self.tz)
         return type(self)(new_values)._with_freq("infer").tz_localize(self.tz)
 
     def to_period(self, freq=None):