For Lot # you need to ask what's the purpose and goal that you want to achieve. for example:
If I want the lot number to be able to be help me with traceability then I need to crate a Lot number with the product Item number (create your own or assigned simple digits for each item), also I want to know when it was produced, and in what shift . ... so for this case I would use the following: I would start with the Item # 25361, then I will include the Julian Date 005 and include the shift that produced it 1 . so my lot number would end up been 253610051 , This can tell me the Item, when it was produced, and what shift This information is important for traceability which is very important for your Recall Plan... but you can go with just Julian date but if you have a complain you going to ask your self or the customer what product is it, and find out on what shift it was produced to set corrective action...and if you want to go the extra mile and if your going to use a LaserJet printer to print the code date. its always better if you include the military time...
So it all depends on how fast you want to be able identify an item...
I helped many companies achieve SQF Level 3, my objective taking the programs the extra mile for food safety and quality.