Many ways to do lot coding. Often times it's done julian style. an example (stolen from the net) could look like:
Sometimes, rather than a specific day of a month, the "Julian date" or day of the year is given --for example, January 1 would be "1" and February 1 would be "32." These two illustrations by the Canned Food Alliance show how this might work:
Can code:2061(February 6, 2001); 2=month, 06=date, 1=year
Can code: 0195(July 14, 2000); 0=year, 195=Julian date -- July 14th is the 195th day of the year
If you run multiple shifts, it's prudent to amend the julian code to include a shift designator (-1/2/3, -A/B/C, etc)