=== modified file 'src/pytz/__init__.py'
--- src/pytz/__init__.py	2015-09-21 13:31:13 +0000
+++ src/pytz/__init__.py	2015-12-05 15:05:32 +0000
@@ -57,7 +57,7 @@
             ...
         UnicodeEncodeError: ...
         """
-        s.encode('US-ASCII') # Raise an exception if not ASCII
+        s.encode('ASCII') # Raise an exception if not ASCII
         return s # But return the original string - not a byte string.
 
 else: # Python 2.x
@@ -73,7 +73,7 @@
             ...
         UnicodeEncodeError: ...
         """
-        return s.encode('US-ASCII')
+        return s.encode('ASCII')
 
 
 def open_resource(name):

=== modified file 'src/pytz/tests/test_docs.py'
--- src/pytz/tests/test_docs.py	2014-03-21 06:12:11 +0000
+++ src/pytz/tests/test_docs.py	2015-12-05 15:06:25 +0000
@@ -13,7 +13,7 @@
         '''Confirm the README.txt is pure ASCII.'''
         f = open(README, 'rb')
         try:
-            f.read().decode('US-ASCII')
+            f.read().decode('ASCII')
         finally:
             f.close()
 

=== modified file 'src/pytz/tzfile.py'
--- src/pytz/tzfile.py	2011-11-04 10:32:42 +0000
+++ src/pytz/tzfile.py	2015-12-05 15:05:50 +0000
@@ -15,13 +15,13 @@
 
 def _byte_string(s):
     """Cast a string or byte string to an ASCII byte string."""
-    return s.encode('US-ASCII')
+    return s.encode('ASCII')
 
 _NULL = _byte_string('\0')
 
 def _std_string(s):
     """Cast a string or byte string to an ASCII string."""
-    return str(s.decode('US-ASCII'))
+    return str(s.decode('ASCII'))
 
 def build_tzinfo(zone, fp):
     head_fmt = '>4s c 15x 6l'