diff --git a/src/ISO8601.cpp b/src/ISO8601.cpp
index 71671072c..2a6ef6ddc 100644
--- a/src/ISO8601.cpp
+++ b/src/ISO8601.cpp
@@ -806,6 +806,18 @@ bool ISO8601d::leapYear (int year)
          ! (year % 400);
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// Static
+int ISO8601d::daysInMonth (int month, int year)
+{
+  static int days[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+
+  if (month == 2 && ISO8601d::leapYear (year))
+    return 29;
+
+  return days[month - 1];
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Static
 int ISO8601d::dayOfWeek (const std::string& input)
diff --git a/src/ISO8601.h b/src/ISO8601.h
index 2ee9b0432..34669e9af 100644
--- a/src/ISO8601.h
+++ b/src/ISO8601.h
@@ -45,6 +45,7 @@ public:
   bool parse (const std::string&, std::string::size_type&, const std::string& format = "");
 
   static bool leapYear (int);
+  static int daysInMonth (int, int);
 
   static int dayOfWeek (const std::string&);
 
diff --git a/test/iso8601d.t.cpp b/test/iso8601d.t.cpp
index bdf3682f0..b3a5bd60d 100644
--- a/test/iso8601d.t.cpp
+++ b/test/iso8601d.t.cpp
@@ -71,7 +71,7 @@ void testParse (
 ////////////////////////////////////////////////////////////////////////////////
 int main (int argc, char** argv)
 {
-  UnitTest t (792);
+  UnitTest t (794);
 
   ISO8601d iso;
   std::string::size_type start = 0;
@@ -224,6 +224,10 @@ int main (int argc, char** argv)
     t.ok    (ISO8601d::leapYear (2000), "2000 is a leap year");
     t.notok (ISO8601d::leapYear (1900), "1900 is not a leap year");
 
+    // Days in month.
+    t.is (ISO8601d::daysInMonth (2, 2008), 29, "29 days in February 2008");
+    t.is (ISO8601d::daysInMonth (2, 2007), 28, "28 days in February 2007");
+
     t.is (ISO8601d::dayOfWeek ("SUNDAY"),    0, "SUNDAY == 0");
     t.is (ISO8601d::dayOfWeek ("sunday"),    0, "sunday == 0");
     t.is (ISO8601d::dayOfWeek ("Sunday"),    0, "Sunday == 0");