Added struct tm to time_point conversion function

Examples-and-Recipes.md

@@ -24,6 +24,30 @@ system_clock::time_point = day_point(ymd) +
                            hours(h) + minutes(min) + seconds(s);
 ```
 
+Alternatively, using `struct tm` to hold the components:
+
+```c++
+// Ignores tm_isdst!
+template <typename Clock, typename Duration>
+void to_time_point(const std::tm& t,
+                   std::chrono::time_point<Clock, Duration>& tp)
+{
+    using namespace std::chrono;
+    using namespace date;
+    // Component values (as obtained from an UI form, for example)
+    int y = t.tm_year + 1900;
+    auto ymd = year(y)/(t.tm_mon+1)/t.tm_mday; // Yields a year_month_day type
+    if (!ymd.ok())
+        throw std::runtime_error("Invalid date");
+    tp =  day_point(ymd) +
+          hours(t.tm_hour) + minutes(t.tm_min) + seconds(t.tm_sec);
+}
+
+std::chrono::system_clock::time_point tp;
+std::tm components = {...};
+to_time_point(components, tp);
+```
+
 <a name="components_to_time_point">
 ### Obtaining `y/m/d h:m:s` components from a `time_point`
 (by [ecorm](https://github.com/ecorm))
@@ -63,7 +87,7 @@ std::tm to_calendar_time(std::chrono::time_point<Clock, Duration> tp)
     result.tm_min   = tod.minutes().count();
     result.tm_hour  = tod.hours().count();
     result.tm_mday  = unsigned(ymd.day());
-    result.tm_mon   = unsigned(ymd.month());
+    result.tm_mon   = unsigned(ymd.month()) - 1u; // Zero-based!
     result.tm_year  = int(ymd.year()) - 1900;
     result.tm_wday  = unsigned(weekday);
     result.tm_yday  = daysSinceJan1.count();