Is the date on the bottom of the bottle a production date or an expiration date?

It is a production/manufacturing date. Hairstory products have a recommended use period of 12 months after opening, consistent with standard Period After Opening (PAO) guidelines for personal care products. If a customer has a significantly old bottle: if the product looks, smells, and feels normal it is generally fine to use; if there are visible changes in color, smell, or texture, discontinue use.