Core: Fix build for vs2014

src/server/shared/Packets/ByteBuffer.h

@@ -390,7 +390,7 @@ class ByteBuffer
             lt.tm_mon = (packedDate >> 20) & 0xF;
             lt.tm_year = ((packedDate >> 24) & 0x1F) + 100;
 
-            return uint32(mktime(&lt) + timezone);
+            return uint32(mktime(&lt) + _timezone);
         }
 
         ByteBuffer& ReadPackedTime(uint32& time)