diff --git a/src/main/java/APCalendar.java b/src/main/java/APCalendar.java
index 6d2ba93..346292f 100644
--- a/src/main/java/APCalendar.java
+++ b/src/main/java/APCalendar.java
@@ -55,7 +55,7 @@ private static int dayOfYear(int month, int day, int year)
    */
   public static int dayOfWeek(int month, int day, int year)
   {
-    int additionalDays = dayOfYear(month, day, year) - 1;
+    int additionalDays = dayOfYear(month, day, year) - firstDayOfYear(year);
     return (firstDayOfYear(year) + additionalDays) % 7;
   }
 }