From aff44caed18973ab96bf924e4eba5475ad5835d6 Mon Sep 17 00:00:00 2001
From: "Adam R. Jensen" <39184289+AdamRJensen@users.noreply.github.com>
Date: Wed, 29 Jul 2026 11:47:35 +0200
Subject: [PATCH 1/3] Simplify conversion of times to midnight

Replaced list comprehension with normalize method to convert times to midnight.
---
 src/solposx/solarposition/usno.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/solposx/solarposition/usno.py b/src/solposx/solarposition/usno.py
index c730ed3..3c49e6d 100644
--- a/src/solposx/solarposition/usno.py
+++ b/src/solposx/solarposition/usno.py
@@ -85,9 +85,7 @@ def usno(times, latitude, longitude, *, delta_t=67.0, gmst_option=1):
     d = asind(sind(e) * sind(L))
 
     # JD_0 is the Julian date of the previous midnight (0h) UT1
-    midnight = pd.DatetimeIndex(
-        [t.replace(hour=0, minute=0, second=0) for t in times_utc]
-    )
+    midnight = times_utc.normalize()  # Convert times to midnight
 
     JD_0 = midnight.to_julian_date()
 

From 2dcffb4e3c7e188ac934d1143fc792668794f13a Mon Sep 17 00:00:00 2001
From: "Adam R. Jensen" <39184289+AdamRJensen@users.noreply.github.com>
Date: Thu, 30 Jul 2026 08:00:30 +0200
Subject: [PATCH 2/3] Trigger tests actions

---
 src/solposx/solarposition/usno.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/solposx/solarposition/usno.py b/src/solposx/solarposition/usno.py
index 3c49e6d..3628da5 100644
--- a/src/solposx/solarposition/usno.py
+++ b/src/solposx/solarposition/usno.py
@@ -85,7 +85,7 @@ def usno(times, latitude, longitude, *, delta_t=67.0, gmst_option=1):
     d = asind(sind(e) * sind(L))
 
     # JD_0 is the Julian date of the previous midnight (0h) UT1
-    midnight = times_utc.normalize()  # Convert times to midnight
+    midnight = times_utc.normalize()  # Convert times_utc to midnight
 
     JD_0 = midnight.to_julian_date()
 

From 4de655986a276ac9afd5db417a324643f6d3620f Mon Sep 17 00:00:00 2001
From: "Adam R. Jensen" <39184289+AdamRJensen@users.noreply.github.com>
Date: Thu, 30 Jul 2026 08:14:14 +0200
Subject: [PATCH 3/3] Update whatsnew.rst

---
 docs/source/whatsnew.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/source/whatsnew.rst b/docs/source/whatsnew.rst
index 16ce46c..d2c7eeb 100644
--- a/docs/source/whatsnew.rst
+++ b/docs/source/whatsnew.rst
@@ -14,6 +14,8 @@ Changed
 ^^^^^^^
 * matplotlib is now an optional ``doc`` dependency instead of a required
   dependency. (:pull:`146`)
+* Add support for correctly handling sub-second timestamp resolution in
+  :py:func:`solposx.solarposition.usno`. (:issue:`156`, :pull:`157`)
 
 Added
 ^^^^^