Date coding rules

So question about date coding

We use letters to indicate year and then the day of that year. ABCDEFG...etc

Last year was F and lets say first day of the year is 01 so F01 indicated january 1st, 2019. G would be 2020.

All of our products expire within 3 years. Nothing more than 3 years. 

Soo this year to make our date codes into letter G for 2020, the machine isnt capable of printing G so we went back to C because the machine is capable of printing C. 

C is the year 2016. And if we made product back in 2016 with date code C, it would have been expired by now since it was 4 years ago.

So from a regulatory standpoint and SQF (if any), is this ACCEPTABLE AND LEGAL? 

Again we have no product with date code C anymore and we want to use C is 2020. 

People can understand your date coding - outside of your own company that is?

I wouldnt imagine they know what does C or G really mean. They would just know its a date code. We have exp date printed next to it.

Question...why not use the expiration date as your "date coding".  This is what practically every company I've worked for does...beverage industry.

If you use the same expiration date for multiple production batches, then perhaps you can come up with another way to code it so you can differentiate between the batches with the same expiration date that you machine can handle.