Hi, thanks for the feedback. If you know the code for year x, you can quickly calculate the code for year x-1 or x+1. If you want to be able to quickly do this for any given year you would have to know the code for every year by heart. I just updated my blog post: Now it contains the year codes from 1800 to 2039. It also contains a small Go script that generates all these year codes and all you need to do if you want more year codes is to adjust the for-loop interval.