Updated Examples and Recipes (markdown)

Examples-and-Recipes.md

@@ -24,6 +24,7 @@ This page contains examples and recipes contributed by community members. Feel f
 - [How many timezones are using daylight saving?](#tz_daylight)
 - [What is the epoch difference between Unix Time and GPS time?](#unix_gps_epoch_diff)
 - [How to convert to/from C++ Builder's TDate and TDateTime](#TDate)
+- [How to convert to/from QDate](#QDate)
 
 ***
 
@@ -1215,6 +1216,30 @@ which outputs:
     -1.25
     35065
 
+<a name="QDate"></a>
+### How to convert to/from QDate
+(by [Howard Hinnant](https://github.com/HowardHinnant))
+
+Here are functions you can use to convert between [`QDate`](http://doc.qt.io/qt-5/qdate.html) and `sys_days`:
+
+    date::sys_days
+    to_sys_days(QDate qd)
+    {
+        using namespace date;
+        return sys_days{days{qd.toJulianDay()} -
+            (sys_days{1970_y/jan/1} - sys_days{year{-4713}/nov/24})};
+    }
+
+    QDate
+    to_QDate(date::sys_days sd)
+    {
+        using namespace date;
+        return QDate::fromJulianDay((sd.time_since_epoch() +
+            (sys_days{1970_y/jan/1} - sys_days{year{-4713}/nov/24})).count());
+    }
+
+These work by simply adjusting the epoch of these two types.
+
 ***
 
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