Remove all internal uses of utcfromtimestamp

Author: pganssle

Lib/email/utils.py

@@ -143,13 +143,13 @@ def formatdate(timeval=None, localtime=False, usegmt=False):
     # 2822 requires that day and month names be the English abbreviations.
     if timeval is None:
         timeval = time.time()
-    if localtime or usegmt:
-        dt = datetime.datetime.fromtimestamp(timeval, datetime.timezone.utc)
-    else:
-        dt = datetime.datetime.utcfromtimestamp(timeval)
+    dt = datetime.datetime.fromtimestamp(timeval, datetime.timezone.utc)
+
     if localtime:
         dt = dt.astimezone()
         usegmt = False
+    elif not usegmt:
+        dt = dt.replace(tzinfo=None)
     return format_datetime(dt, usegmt)
 
 def format_datetime(dt, usegmt=False):

Lib/test/test_plistlib.py

@@ -925,7 +925,7 @@ def test_large_timestamp(self):
         # Issue #26709: 32-bit timestamp out of range
         for ts in -2**31-1, 2**31:
             with self.subTest(ts=ts):
-                d = (datetime.datetime.utcfromtimestamp(0) +
+                d = (datetime.datetime(1970, 1, 1, 0, 0) +
                      datetime.timedelta(seconds=ts))
                 data = plistlib.dumps(d, fmt=plistlib.FMT_BINARY)
                 self.assertEqual(plistlib.loads(data), d)