Changes

##Field for expiration date (already existing).

##Field for expiration date (already existing).

##Field for the entry date of the expiration date (not yet existing, which is a current data quality issue).

##Field for the entry date of the expiration date (not yet existing, which is a current data quality issue).

#'''Comparison of declared shelf life between products.''' The "Shelf Life" (German: "Haltbarkeit") tab of the OFF app would contain an article explaining edibility, proper storage etc. and below that an auto-generated section summarizing results inferred from best-before and use-by dates of products in this category. That would include a comparison of the scanned product with other products in the category, showing if there are "better" ones (lasting longer, also without preservatives). This is basically small advertising for products that are not labelled to be thrown away, hopefully nudging manufacturers to provide more real best-before dates.  The OFF web interface already has a nice architecture for product comparison with product in the same category. Comparison of the expiration period can be added there easily. See for example [https://world.openfoodfacts.org/product/4001686386613 here] at "Comparison to average values of products in the same category: …".  This idea has been discussed before by OFF: "[…] a user inputting production and consumption dates for the same product at the same time would enable us to make averages over time […] that could help see producers which are too conservative […] assuming that all products rot at the same pace (all products that are similar)" (@teolemon [https://openfoodfacts.slack.com/archives/C17324N0L/p1462730965000039) here]).

#'''Comparison of declared shelf life between products.''' The "Shelf Life" (German: "Haltbarkeit") tab of the OFF app would contain an article explaining edibility, proper storage etc. and below that an auto-generated section summarizing results inferred from best-before and use-by dates of products in this category. That would include a comparison of the scanned product with other products in the category, showing if there are "better" ones (lasting longer, also without preservatives). This is basically small advertising for products that are not labelled to be thrown away, hopefully nudging manufacturers to provide more real best-before dates.  The OFF web interface already has a nice architecture for product comparison with product in the same category. Comparison of the expiration period can be added there easily. See for example [https://world.openfoodfacts.org/product/4001686386613 here] at "Comparison to average values of products in the same category: …".  This idea has been discussed before by OFF: "[…] a user inputting production and consumption dates for the same product at the same time would enable us to make averages over time […] that could help see producers which are too conservative […] assuming that all products rot at the same pace (all products that are similar)" (@teolemon [https://openfoodfacts.slack.com/archives/C17324N0L/p1462730965000039) here]).

# '''Counter for rescued food.''' Basically a feedback form at the bottom of the knowledge article about a food item's storage life, saying: "Did this help you to decide if your food item is still good to eat?", with the following options to answer: "Yes, and I saved it." / "Yes, but I had to throw it away." / "No, I'm still not sure." From this, detailed statistics about the rescued food can be made, including the weight, caloric energy content, approximate market price and approximate embodied carbon emissions of the rescued food. This makes it simple to argue for the success and continuous development of this feature.

# '''Counter for rescued food.''' Basically a feedback form at the bottom of the knowledge article about a food item's storage life, saying: "Did this help you to decide if your food item is still good to eat?", with the following options to answer: "Yes, and I saved it." / "Yes, but I had to throw it away." / "No, I'm still not sure." From this, detailed statistics about the rescued food can be made, including the weight, caloric energy content, approximate market price and approximate embodied carbon emissions of the rescued food. This makes it simple to argue for the success and continuous development of this feature.