Go to the Appliance 411 website (www.appliance411.com), which allows you to date a home appliance by its serial number.
Select the brand, appliance type, location and serial and model number of your freezer in the "Enter Product Details" box, then click "Date it!" Be sure to include any letter prefixes before the serial/model numbers.
Read the date of your freezer if it gives you a year. If you don't get a result, check your numbers to make sure you aren't confusing letters with numbers. If you still don't get a result, you will have to contact your freezer manufacturer.