From 2d16863717c82457522aa915249ba185df79a9c2 Mon Sep 17 00:00:00 2001
From: Richard Shadrach <45562402+rhshadrach@users.noreply.github.com>
Date: Fri, 22 Sep 2023 10:59:38 -0400
Subject: [PATCH] PERF: Add type-hints in tzconversion.pyx (#55241)

---
 doc/source/whatsnew/v2.2.0.rst       | 2 +-
 pandas/_libs/tslibs/tzconversion.pyx | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/doc/source/whatsnew/v2.2.0.rst b/doc/source/whatsnew/v2.2.0.rst
index 8eab623a2b5f7..ebca1605be8d5 100644
--- a/doc/source/whatsnew/v2.2.0.rst
+++ b/doc/source/whatsnew/v2.2.0.rst
@@ -238,7 +238,7 @@ Performance improvements
 - Performance improvement in :meth:`DataFrame.sort_index` and :meth:`Series.sort_index` when indexed by a :class:`MultiIndex` (:issue:`54835`)
 - Performance improvement in :meth:`Index.difference` (:issue:`55108`)
 - Performance improvement when indexing with more than 4 keys (:issue:`54550`)
--
+- Performance improvement when localizing time to UTC (:issue:`55241`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_220.bug_fixes:
diff --git a/pandas/_libs/tslibs/tzconversion.pyx b/pandas/_libs/tslibs/tzconversion.pyx
index e17d264333264..a96779aa33255 100644
--- a/pandas/_libs/tslibs/tzconversion.pyx
+++ b/pandas/_libs/tslibs/tzconversion.pyx
@@ -462,7 +462,7 @@ cdef str _render_tstamp(int64_t val, NPY_DATETIMEUNIT creso):
 
 
 cdef _get_utc_bounds(
-    ndarray vals,
+    ndarray[int64_t] vals,
     int64_t* tdata,
     Py_ssize_t ntrans,
     const int64_t[::1] deltas,
@@ -472,7 +472,7 @@ cdef _get_utc_bounds(
     # result_a) or right of the DST transition (store in result_b)
 
     cdef:
-        ndarray result_a, result_b
+        ndarray[int64_t] result_a, result_b
         Py_ssize_t i, n = vals.size
         int64_t val, v_left, v_right
         Py_ssize_t isl, isr, pos_left, pos_right