diff --git a/src/saneyaml.py b/src/saneyaml.py
index eb0c19f..dcc5903 100644
--- a/src/saneyaml.py
+++ b/src/saneyaml.py
@@ -327,7 +327,7 @@ def is_float(s):
 
 
 # Return True if s is an iso date such as `2019-12-12`
-is_iso_date = re.compile(r'19|20[0-9]{2}-[0-1][0-9]-[0-3]?[1-9]').match
+is_iso_date = re.compile(r'(19|20)[0-9]{2}-[0-1][0-9]-[0-3][0-9]').match
 
 SaneDumper.add_representer(int, SaneDumper.string_dumper)
 SaneDumper.add_representer(dict, SaneDumper.ordered_dumper)
diff --git a/tests/test_saneyaml.py b/tests/test_saneyaml.py
index bd296a7..d0e704c 100644
--- a/tests/test_saneyaml.py
+++ b/tests/test_saneyaml.py
@@ -137,6 +137,22 @@ def test_load_ignore_aliases(self):
         ])
         assert  expected == result
 
+    def test_is_iso_date(self):
+        assert saneyaml.is_iso_date('1994-01-01')
+        assert saneyaml.is_iso_date('2004-01-01')
+        assert not saneyaml.is_iso_date('1800-01-01')
+        assert not saneyaml.is_iso_date('2100-01-01')
+        assert saneyaml.is_iso_date('2004-01-30')
+        assert not saneyaml.is_iso_date('2004-01-40')
+        assert not saneyaml.is_iso_date('2004-01-4')
+        assert not saneyaml.is_iso_date('2004-01-3a')
+        assert not saneyaml.is_iso_date('1994-01-1')
+        assert not saneyaml.is_iso_date('1994-1-1')
+        assert not saneyaml.is_iso_date('193')
+        # Hey, nothing's perfect
+        assert saneyaml.is_iso_date('2003-02-29')
+        assert saneyaml.is_iso_date('2004-01-35')
+
 
 safe_chars = re.compile(r'[\W_]', re.MULTILINE)