Retain a limit on both ends, mark where we might return a null instead.

src/libmdb/data.c

@@ -894,10 +894,9 @@ mdb_date_to_tm(double td, struct tm *t)
 	long yr, q;
 	const int *cal;
 
-	// if you want to limit 1900--2700, do this
-	// but it's not necessary
-	// if (td < 0.0 || td > 1e6) // About 2700 AD
-	// 	return;
+	// limit to ~1100AD--2700A to protect from overflow
+	if (td < -1e6 || td > 1e6)
+		return;
 
 	yr = 1;
 	day = (long)(td);
@@ -947,6 +946,8 @@ mdb_date_to_string(MdbHandle *mdb, const char *fmt, void *buf, int start)
 
 	mdb_date_to_tm(td, &t);
 
+	// check if t is still unchanged, return empty string?
+
 	strftime(text, mdb->bind_size, mdb->date_fmt, &t);
 
 	return text;