From 8bdba2a1537d3d0cecefa629febaa6ecf2d30041 Mon Sep 17 00:00:00 2001
From: "P. L. Lim" <2090236+pllim@users.noreply.github.com>
Date: Thu, 21 Sep 2023 20:23:13 -0400
Subject: [PATCH] Backport PR #15298: Address ruff's DTZ003 rule violations

---
 astropy/time/core.py             | 10 +++++-----
 astropy/time/tests/test_basic.py |  7 +++++--
 astropy/utils/iers/iers.py       |  6 ++++--
 docs/conf.py                     |  4 ++--
 4 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/astropy/time/core.py b/astropy/time/core.py
index 896940f3105..f6d2ae787c1 100644
--- a/astropy/time/core.py
+++ b/astropy/time/core.py
@@ -11,7 +11,7 @@
 import operator
 import os
 import threading
-from datetime import date, datetime, timedelta
+from datetime import date, datetime, timedelta, timezone
 from time import strftime
 from warnings import warn
 
@@ -1930,10 +1930,10 @@ def now(cls):
         method is called.
 
         .. note::
-            "Now" is determined using the `~datetime.datetime.utcnow`
+            "Now" is determined using the `~datetime.datetime.now`
             function, so its accuracy and precision is determined by that
             function.  Generally that means it is set by the accuracy of
-            your system clock.
+            your system clock. The timezone is set to UTC.
 
         Returns
         -------
@@ -1941,8 +1941,8 @@ def now(cls):
             A new `Time` object (or a subclass of `Time` if this is called from
             such a subclass) at the current time.
         """
-        # call `utcnow` immediately to be sure it's ASAP
-        dtnow = datetime.utcnow()
+        # call `now` immediately to be sure it's ASAP
+        dtnow = datetime.now(tz=timezone.utc)
         return cls(val=dtnow, format="datetime", scale="utc")
 
     info = TimeInfo()
diff --git a/astropy/time/tests/test_basic.py b/astropy/time/tests/test_basic.py
index a06aead92ec..356598b229a 100644
--- a/astropy/time/tests/test_basic.py
+++ b/astropy/time/tests/test_basic.py
@@ -1475,7 +1475,10 @@ def test_now():
     Tests creating a Time object with the `now` class method.
     """
 
-    now = datetime.datetime.utcnow()
+    # `Time.datetime` is not timezone aware, meaning `.replace` is necessary for
+    # `now` also not be timezone aware.
+    now = datetime.datetime.now(tz=datetime.timezone.utc).replace(tzinfo=None)
+
     t = Time.now()
 
     assert t.format == "datetime"
@@ -1483,7 +1486,7 @@ def test_now():
 
     dt = t.datetime - now  # a datetime.timedelta object
 
-    # this gives a .1 second margin between the `utcnow` call and the `Time`
+    # this gives a .1 second margin between the `now` call and the `Time`
     # initializer, which is really way more generous than necessary - typical
     # times are more like microseconds.  But it seems safer in case some
     # platforms have slow clock calls or something.
diff --git a/astropy/utils/iers/iers.py b/astropy/utils/iers/iers.py
index 1ea3903456a..c4c1d9df138 100644
--- a/astropy/utils/iers/iers.py
+++ b/astropy/utils/iers/iers.py
@@ -10,7 +10,7 @@
 """
 
 import re
-from datetime import datetime
+from datetime import datetime, timezone
 from urllib.parse import urlparse
 from warnings import warn
 
@@ -1077,7 +1077,9 @@ def open(cls, file=None, cache=False):
     def _today():
         # Get current day in scale='tai' without going through a scale change
         # (so we do not need leap seconds).
-        s = "{0.year:04d}-{0.month:02d}-{0.day:02d}".format(datetime.utcnow())
+        s = "{0.year:04d}-{0.month:02d}-{0.day:02d}".format(
+            datetime.now(tz=timezone.utc)
+        )
         return Time(s, scale="tai", format="iso", out_subfmt="date")
 
     @classmethod
diff --git a/docs/conf.py b/docs/conf.py
index 7992e23358c..49a65fdecd2 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -28,7 +28,7 @@
 import doctest
 import os
 import sys
-from datetime import datetime
+from datetime import datetime, timezone
 from importlib import metadata
 
 from packaging.requirements import Requirement
@@ -208,7 +208,7 @@
 
 project = "Astropy"
 author = "The Astropy Developers"
-copyright = f"2011–{datetime.utcnow().year}, " + author
+copyright = f"2011–{datetime.now(tz=timezone.utc).year}, " + author
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the