diff -r b7e9f5c65e30 -r adf5a495f0e2 src/ai/api/ai_subsidy.cpp
--- a/src/ai/api/ai_subsidy.cpp	Fri Apr 25 00:22:41 2008 +0000
+++ b/src/ai/api/ai_subsidy.cpp	Fri Apr 25 07:06:57 2008 +0000
@@ -43,8 +43,8 @@
 		month += 12 - _subsidies[subsidy_id].age;
 	}
 
-	year += month / 12;
-	month = month % 12;
+	year += (month - 1) / 12;
+	month = ((month - 1) % 12) + 1;
 
 	return AIDate::GetDate(year, month, 1);
 }