feat: display car age

CarManagerV3/Car.cs

@@ -19,6 +19,7 @@ namespace CarManagerV3
         private int mileage;
         private decimal price;
         private int order;
+        private int age;
 
         public int Id { get => id; 
             set {
@@ -46,9 +47,7 @@ namespace CarManagerV3
         public int Year { get => year; 
             set
             {
-                
                 if (value < 1886 || value > DateTime.Now.Year + 1) throw new ArgumentException("Year must be between 1886 and next year.");
-                Console.WriteLine($"Updating year to {year}");
                 year = value;
             }
         }
@@ -79,6 +78,19 @@ namespace CarManagerV3
 
         public int Order { get => order; set => order = value; }
 
+        public int Age { get => DateTime.Now.Year - year; }
+        public string AgeString
+        {
+            get
+            {
+                int age = this.Age;
+                if (age == 0) return "New";
+                else if (age == 1) return "1 year";
+                else if (age < 0) return "From the future!";
+                else return $"{age} years";
+            }
+        }
+
         //TODO: Make Id read-only CUID. Allows for better integrity, especially when merging.
         //TODO: Add buying price and automatic calculation of profit/loss with selling price suggestion.
         //TODO: Add Buying Date.