1 files changed, 6 insertions, 4 deletions
diff --git a/date.h b/date.h
index 1b5288599..58f952a19 100644
--- a/date.h
+++ b/date.h
@@ -24,14 +24,16 @@
  * The offset in days from the '_date == 0' till
  * 'ConvertYMDToDate(ORIGINAL_BASE_YEAR, 0, 1)'
  */
-#define DAYS_TILL_ORIGINAL_BASE_YEAR 0
+#define DAYS_TILL_ORIGINAL_BASE_YEAR (365 * ORIGINAL_BASE_YEAR + ORIGINAL_BASE_YEAR / 4 - ORIGINAL_BASE_YEAR / 100 + ORIGINAL_BASE_YEAR / 400)
 
 /* Temporary value to make transition to full past 2090 easier/more clear */
-#define BASE_YEAR 1920
+#define BASE_YEAR 0
 
 /* The absolute minimum & maximum years in OTTD */
-#define MIN_YEAR 1920
-#define MAX_YEAR 2090
+#define MIN_YEAR 0
+/* MAX_YEAR, nicely rounded value of the number of years that can
+ * be encoded in a single 32 bits date, about 2^31 / 366 years. */
+#define MAX_YEAR 5000000
 
 /* Year and Date are defined elsewhere */
 typedef uint8  Month;