diff --git a/src/common/datetime.cpp b/src/common/datetime.cpp
index e20225d593..3f036e61da 100644
--- a/src/common/datetime.cpp
+++ b/src/common/datetime.cpp
@@ -2054,16 +2054,22 @@ wxDateTime::wxDateTime_t wxDateTime::GetWeekOfMonth(wxDateTime::WeekFlags flags,
                                                     const TimeZone& tz) const
 {
     Tm tm = GetTm(tz);
-    wxDateTime dtMonthStart = wxDateTime(1, tm.mon, tm.year);
-    int nWeek = GetWeekOfYear(flags) - dtMonthStart.GetWeekOfYear(flags) + 1;
-    if ( nWeek < 0 )
+    const wxDateTime dateFirst = wxDateTime(1, tm.mon, tm.year);
+    const wxDateTime::WeekDay wdFirst = dateFirst.GetWeekDay();
+
+    if ( flags == Default_First )
     {
-        // this may happen for January when Jan, 1 is the last week of the
-        // previous year
-        nWeek += IsLeapYear(tm.year - 1) ? 53 : 52;
+        flags = GetCountry() == USA ? Sunday_First : Monday_First;
     }
 
-    return (wxDateTime::wxDateTime_t)nWeek;
+    // compute offset of dateFirst from the beginning of the week
+    int firstOffset;
+    if ( flags == Sunday_First )
+        firstOffset = wdFirst - Sun;
+    else
+        firstOffset = wdFirst == Sun ? DAYS_PER_WEEK - 1 : wdFirst - Mon;
+
+    return (wxDateTime::wxDateTime_t)((tm.mday - 1 + firstOffset)/7 + 1);
 }
 
 wxDateTime& wxDateTime::SetToYearDay(wxDateTime::wxDateTime_t yday)
diff --git a/tests/datetime/datetimetest.cpp b/tests/datetime/datetimetest.cpp
index 6cddf64142..4731265645 100644
--- a/tests/datetime/datetimetest.cpp
+++ b/tests/datetime/datetimetest.cpp
@@ -555,6 +555,8 @@ for n in range(20):
         { { 16, wxDateTime::Oct, 1942, 0, 0, 0, 0.0, wxDateTime::Inv_WeekDay, 0 }, 42, 3, 3, 289 },
         { { 30, wxDateTime::Dec, 2003, 0, 0, 0, 0.0, wxDateTime::Inv_WeekDay, 0 },  1, 5, 5, 364 },
         { {  2, wxDateTime::Jan, 2004, 0, 0, 0, 0.0, wxDateTime::Inv_WeekDay, 0 },  1, 1, 1,   2 },
+        { {  5, wxDateTime::Jan, 2010, 0, 0, 0, 0.0, wxDateTime::Inv_WeekDay, 0 },  1, 2, 2,   5 },
+        { {  3, wxDateTime::Jan, 2011, 0, 0, 0, 0.0, wxDateTime::Inv_WeekDay, 0 },  1, 2, 2,   3 },
     };
 
     for ( size_t n = 0; n < WXSIZEOF(weekNumberTestDates); n++ )
@@ -570,10 +572,14 @@ for n in range(20):
             wmon2 = dt.GetWeekOfMonth(wxDateTime::Sunday_First),
             dnum = dt.GetDayOfYear();
 
-        CPPUNIT_ASSERT_EQUAL( wn.dnum, dnum );
-        CPPUNIT_ASSERT_EQUAL( wn.wmon, wmon );
-        CPPUNIT_ASSERT_EQUAL( wn.wmon2, wmon2 );
-        CPPUNIT_ASSERT_EQUAL( wn.week, week );
+        WX_ASSERT_EQUAL_MESSAGE( ("day of year for %s", d.Format()),
+                                 wn.dnum, dnum );
+        WX_ASSERT_EQUAL_MESSAGE( ("week of month (Monday) for %s", d.Format()),
+                                 wn.wmon, wmon );
+        WX_ASSERT_EQUAL_MESSAGE( ("week of month (Sunday) for %s", d.Format()),
+                                 wn.wmon2, wmon2 );
+        WX_ASSERT_EQUAL_MESSAGE( ("week of year for %s", d.Format()),
+                                 wn.week, week );
 
         int year = d.year;
         if ( week == 1 && d.month != wxDateTime::Jan )