utils: Rename/Add date functions

utils.h

@@ -81,7 +81,9 @@ inline unsigned int toUInt(const std::string &str)
 	return result;
 }
 
+std::string formatLocalDate(time_t t, std::string format);
 std::string toISODate(time_t t);
+std::string toISODateTime(time_t t);
 
 template <class T> inline std::string toString(const T &v)
 {