adds yearday functionality

Time.cpp

@@ -120,7 +120,30 @@ int weekday(time_t t) {
   refreshCache(t);
   return tm.Wday;
 }
-
+
+int yearday(time_t t) {
+  tmElements_t tm;
+  breakTime(t, tm);
+  uint32_t y = tm.Year;
+  int m = tm.Month;
+  int d = tm.Day;
+
+  #define LEAP_YEAR(Y)     ( ((0+(Y))>0) && !((1970+(Y))%4) && ( ((1970+(Y))%100) || !((1970+(Y))%400) ) )
+
+  static  const uint8_t monthDays[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; // API starts months from 1, this array starts from 0
+
+  uint16_t days = d;
+  for (uint8_t i = 1; i < m; i++)
+    days += monthDays[i - 1];
+  if (m > 2 && LEAP_YEAR(y))
+    days++;
+  return days;
+}
+
+int yearday() {
+  return yearday(now());
+}
+
 int month(){
   return month(now()); 
 }

TimeLib.h

@@ -112,6 +112,8 @@ int     day();             // the day now
 int     day(time_t t);     // the day for the given time
 int     weekday();         // the weekday now (Sunday is day 1) 
 int     weekday(time_t t); // the weekday for the given time 
+int     yearday();         // the yearday now
+int     yearday(time_t t); // the yearday for the given time
 int     month();           // the month now  (Jan is month 1)
 int     month(time_t t);   // the month for the given time
 int     year();            // the full four digit year: (2009, 2010 etc)