diff --git a/include/wx/datetime.h b/include/wx/datetime.h
index 49aa4d6dc6..286155f29f 100644
--- a/include/wx/datetime.h
+++ b/include/wx/datetime.h
@@ -462,7 +462,9 @@ public:
         //     instead of modifying the member fields directly!
     struct WXDLLIMPEXP_BASE Tm
     {
-        wxDateTime_t msec, sec, min, hour, mday;
+        wxDateTime_t msec, sec, min, hour,
+                     mday,  // Day of the month in 1..31 range.
+                     yday;  // Day of the year in 0..365 range.
         Month mon;
         int year;
 
@@ -497,9 +499,10 @@ public:
         // the timezone we correspond to
         TimeZone m_tz;
 
-        // these values can't be accessed directly because they're not always
-        // computed and we calculate them on demand
-        wxDateTime_t wday, yday;
+        // This value can only be accessed via GetWeekDay() and not directly
+        // because it's not always computed when creating this object and may
+        // need to be calculated on demand.
+        wxDateTime_t wday;
     };
 
     // static methods
diff --git a/interface/wx/datetime.h b/interface/wx/datetime.h
index 82b744d995..ab0adf6e59 100644
--- a/interface/wx/datetime.h
+++ b/interface/wx/datetime.h
@@ -244,6 +244,42 @@ public:
     };
 
 
+    /**
+        Contains broken down date-time representation.
+
+        This struct is analogous to standard C <code>struct tm</code> and uses
+        the same, not always immediately obvious, conventions for its members:
+        notably its mon and mday fields count from 0 while yday counts from 1.
+     */
+    struct Tm
+    {
+        wxDateTime_t msec,  ///< Number of milliseconds.
+                     sec,   ///< Seconds in 0..59 (60 with leap seconds) range.
+                     min,   ///< Minutes in 0..59 range.
+                     hour,  ///< Hours since midnight in 0..23 range.
+                     mday,  ///< Day of the month in 1..31 range.
+                     yday;  ///< Day of the year in 0..365 range.
+        Month mon;          ///< Month, as an enumerated constant.
+        int year;           ///< Year.
+
+        /**
+            Check if the given date/time is valid (in Gregorian calendar).
+
+            Return @false if the components don't correspond to a correct date.
+         */
+        bool IsValid() const;
+
+        /**
+            Return the week day corresponding to this date.
+
+            Unlike the other fields, the week day is not always available and
+            so must be accessed using this method as it is computed on demand
+            when it is called.
+         */
+        WeekDay GetWeekDay();
+    };
+
+
     /**
         @name Constructors, Assignment Operators and Setters
 
diff --git a/src/common/datetime.cpp b/src/common/datetime.cpp
index eecee09de4..4e0ea0fa69 100644
--- a/src/common/datetime.cpp
+++ b/src/common/datetime.cpp
@@ -1616,6 +1616,7 @@ wxDateTime::Tm wxDateTime::GetTm(const TimeZone& tz) const
     // construct Tm from these values
     Tm tm;
     tm.year = (int)year;
+    tm.yday = (wxDateTime_t)(dayOfYear - 1); // use C convention for day number
     tm.mon = (Month)(month - 1); // algorithm yields 1 for January, not 0
     tm.mday = (wxDateTime_t)day;
     tm.msec = (wxDateTime_t)(timeOnly % 1000);