Index: src/newgrf.cpp
===================================================================
--- src/newgrf.cpp	(revision 18542)
+++ src/newgrf.cpp	(working copy)
@@ -4476,6 +4476,9 @@
 				(log_X << 12) | (log_Y << 8) | (log_X + log_Y);
 		}
 
+		/* -reserve- for day length */
+		case 0x14: return 0;
+
 		default:
 			grfmsg(2, "ParamSet: Unknown Patch variable 0x%02X.", param);
 			return 0;