fixed issue #173 - timezone as output by %z option has a double negative sign

include/spdlog/details/pattern_formatter_impl.h

@@ -317,8 +317,10 @@ public:
 
         int h = total_minutes / 60;
         int m = total_minutes % 60;
-        char sign = h >= 0 ? '+' : '-';
-        msg.formatted << sign;
+        if (h >= 0) //minus sign will be printed anyway if negative
+        {
+            msg.formatted << '+';
+        }
         pad_n_join(msg.formatted, h, m, ':');
     }
 private:
@@ -481,7 +483,7 @@ inline void spdlog::pattern_formatter::handle_flag(char flag)
 {
     switch (flag)
     {
-        // logger name
+    // logger name
     case 'n':
         _formatters.push_back(std::unique_ptr<details::flag_formatter>(new details::name_formatter()));
         break;