The most common Mopar Date Codes are the 4 digit Julian Perpetual Day Calendar. The first 3 numbers are the day of the year and the last number is the year.
Example: 0682 would be the 68th day of 1972 = March 8th 1972. Typically production Model Years for Cuda’s & Challenger’s would be from August 1st to July 31st.
Barracuda & Challenger parts that use the 4 digit Date Code: K-Frame, Seat Tags, Master Cylinder, Power Steering, Wiper Motor, Holley Carb, Carter Carb ID tag, AC Dryer, Hoses, Radiator Support Bracket, Hood Catch , Hood Latch, Emergency Brake, Radio, Key Buzzer Switch, Power Steering Pulley, Power Steering Hose, Heater Blower Motor, Fuel Relay, Radio Crossover, Speedo, Dash Cluster Housing, Tach, Power Steering coolers, Heater Box, Speaker, Rear End, Intake, Heads, Dimmer Switch, Fuel Sender, AC Clutch, and many more.
Here’s some sample photos of the date codes in use: