DEF Date Code
The date code on the BlueDEF box
GA153590089
break this down into 4 groups of numbers:
GA: The designator of the plant that manufactured the DEF
15: The year of manufacture plus 1, so this DEF was made in 2014
359: 365-359 = 6, so the 6th day of the year, or January 6th.
0089...