Use by date best by date

[JoJo]

 When determining the shelf life of food do you merge the date stamped on the package to the reported shelf life or is it plus the stamped date? Such as a can of peanut better says use by 01/01/2018 and the reported shelf life is 3 years is the shelf life date 01/01/2021 or 01/01/2019 (years 17,18, and 19)?
 If it is merged that would greatly shorten perceived shelf to a lot of preppers. 

[Kbop]

there is a pretty simple method to sort that - assuming you aren't trying to store more than a years worth of food.  select shelf stable foods. Eat the oldest and rotate the newest into your pantry.
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the 'best by' and 'use by' dates are a marketing/nutritional thing referring to texture, taste and nutrition.
there are alot of things that can affect shelf life.  so you need to adjust fire accordingly. 
I have salt in my pantry - expired - i check the packaging and make sure its in good shape.  Salt wont go 'stale' or bad over time.  but if the packaging gets damaged or wet or contaminated, its time to replace it.
- this is regular iodized and non iodized and mineral salt, not flavoring salt. (not like onion or garlic salt).

peanut butter is a different animal.  the fats in the mix will make it break down faster over time.  even if you store it perfectly, the slow breakdown of the oils will continue.  There will be variations by brand (think manufacturing method and mix and packaging).  So rotate your stock.

i did try powdered PB - there are posts about this.  One note about powdered PB, there isn't much fat (oil) in that mix and this adds to the shelf life but removes one of its important nutritional components.

[Nemo]

Store and rotate the jar PB.  Maintain the powdered also.  Mix the powder, after brought back to life about 3 to 1* to the jar stuff.  Tastes great, nutritional defects are minimized and its Peanut Butter.  The Ambrosia of the Gods.*


Nemo

*3 parts powder to 1 part jar

*Beer is the Nectar.

[thatGuy]

Great question, no clue..