fix migrations

src/main/java/cc/fascinated/bat/features/birthday/UserBirthday.java

@@ -5,6 +5,7 @@ import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.Setter;
 
+import java.util.Calendar;
 import java.util.Date;
 
 /**
@@ -24,4 +25,25 @@ public class UserBirthday {
      * If the birthday should be hidden
      */
     private boolean hidden;
+
+    /**
+     * Calculates the age of the user
+     *
+     * @return the age of the user
+     */
+    public int calculateAge() {
+        Calendar birthdayCalendar = Calendar.getInstance();
+        birthdayCalendar.setTime(this.getBirthday());
+
+        Calendar today = Calendar.getInstance();
+
+        int age = today.get(Calendar.YEAR) - birthdayCalendar.get(Calendar.YEAR);
+
+        // Check if the birthday hasn't occurred yet this year
+        if (today.get(Calendar.DAY_OF_YEAR) < birthdayCalendar.get(Calendar.DAY_OF_YEAR)) {
+            age--;
+        }
+
+        return age;
+    }
 }