diff -r 5673cf852daa Lib/calendar.py
--- a/Lib/calendar.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/calendar.py	Sat Oct 01 23:46:38 2016 +0000
@@ -111,8 +111,10 @@
 
 
 def weekday(year, month, day):
-    """Return weekday (0-6 ~ Mon-Sun) for year (1970-...), month (1-12),
-       day (1-31)."""
+    """Return weekday (0-6 ~ Mon-Sun) for year (MINYEAR-MAXYEAR),
+       month (1-12), day (1-31)."""
+    if not datetime.MINYEAR <= year <= datetime.MAXYEAR:
+        year = 2000 + year % 400
     return datetime.date(year, month, day).weekday()
 
 
diff -r 5673cf852daa Lib/test/test_calendar.py
--- a/Lib/test/test_calendar.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_calendar.py	Sat Oct 01 23:46:38 2016 +0000
@@ -9,6 +9,56 @@
 import datetime
 import os
 
+# From https://en.wikipedia.org/wiki/Leap_year_starting_on_Saturday
+result_0_02_text = """\
+     February 0
+Mo Tu We Th Fr Sa Su
+    1  2  3  4  5  6
+ 7  8  9 10 11 12 13
+14 15 16 17 18 19 20
+21 22 23 24 25 26 27
+28 29
+"""
+
+result_0_text = """\
+                                   0
+
+      January                   February                   March
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+                1  2          1  2  3  4  5  6             1  2  3  4  5
+ 3  4  5  6  7  8  9       7  8  9 10 11 12 13       6  7  8  9 10 11 12
+10 11 12 13 14 15 16      14 15 16 17 18 19 20      13 14 15 16 17 18 19
+17 18 19 20 21 22 23      21 22 23 24 25 26 27      20 21 22 23 24 25 26
+24 25 26 27 28 29 30      28 29                     27 28 29 30 31
+31
+
+       April                      May                       June
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+                1  2       1  2  3  4  5  6  7                1  2  3  4
+ 3  4  5  6  7  8  9       8  9 10 11 12 13 14       5  6  7  8  9 10 11
+10 11 12 13 14 15 16      15 16 17 18 19 20 21      12 13 14 15 16 17 18
+17 18 19 20 21 22 23      22 23 24 25 26 27 28      19 20 21 22 23 24 25
+24 25 26 27 28 29 30      29 30 31                  26 27 28 29 30
+
+        July                     August                  September
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+                1  2          1  2  3  4  5  6                   1  2  3
+ 3  4  5  6  7  8  9       7  8  9 10 11 12 13       4  5  6  7  8  9 10
+10 11 12 13 14 15 16      14 15 16 17 18 19 20      11 12 13 14 15 16 17
+17 18 19 20 21 22 23      21 22 23 24 25 26 27      18 19 20 21 22 23 24
+24 25 26 27 28 29 30      28 29 30 31               25 26 27 28 29 30
+31
+
+      October                   November                  December
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+                   1             1  2  3  4  5                   1  2  3
+ 2  3  4  5  6  7  8       6  7  8  9 10 11 12       4  5  6  7  8  9 10
+ 9 10 11 12 13 14 15      13 14 15 16 17 18 19      11 12 13 14 15 16 17
+16 17 18 19 20 21 22      20 21 22 23 24 25 26      18 19 20 21 22 23 24
+23 24 25 26 27 28 29      27 28 29 30               25 26 27 28 29 30 31
+30 31
+"""
+
 result_2004_01_text = """\
     January 2004
 Mo Tu We Th Fr Sa Su
@@ -337,12 +387,20 @@
             self.normalize_calendar(calendar.calendar(2004)),
             self.normalize_calendar(result_2004_text)
         )
+        self.assertEqual(
+            self.normalize_calendar(calendar.calendar(0)),
+            self.normalize_calendar(result_0_text)
+        )
 
     def test_output_textcalendar(self):
         self.assertEqual(
             calendar.TextCalendar().formatyear(2004),
             result_2004_text
         )
+        self.assertEqual(
+            calendar.TextCalendar().formatyear(0),
+            result_0_text
+        )
 
     def test_output_htmlcalendar_encoding_ascii(self):
         self.check_htmlcalendar_encoding('ascii', 'ascii')
@@ -387,6 +445,10 @@
             calendar.TextCalendar().formatmonth(2004, 1),
             result_2004_01_text
         )
+        self.assertEqual(
+            calendar.TextCalendar().formatmonth(0, 2),
+            result_0_02_text
+        )
 
     def test_formatmonthname_with_year(self):
         self.assertEqual(