It is easy to identify the production date of Sanyo 18650 cells by checking the manufacture date code. Please note the date code on original Sanyo cells are stamped, but not printed. For example, Sanyo NCR18650GA 3450mAh 3.6V:
1. Old version date code: P02A
The first letter "P" = Year (J=2005; K=2006; L=2007; ... P=2011; Q=2012; R=2013, and so on...)
The last 3 codes = Week (02A means the second week)
Conclusion, code: P02A means the battery made in 2011, the second week.
2. New version date code: 6326
The first number "6" = Year (15=5; 16=6; 17=7; 18=8, and so on...)
The second number "3" = Month (JAN=1; FEB=2; ... SEP=9; OCT=X; NOV=Y; DEC=Z)
The third and fourth number "26" = Day (1st=01; 2nd=02; ... 30th=30; 31st=31)
Conclusion, code: 6326 means the battery made in 26th. March. 2016.