Can you please post pictures and tell how you calculated their age?
By Digi-key's own repack label, dated 2013. I'll try decipher the date codes as well.
I am surprised you received stock this old. This is a question for Digi-Key: can they explain why your parts date back to 2013.
In manufacturing and distribution, First-In-First-Out handling of inventory is a big deal, and normally it's strictly enforced. No system is perfect -
old stock, can, incorrectly, get stranded in the warehouse, while newer stock (of the same item) continues to ship as normal. Stocktakes usually pick
this up, but not always.
An example of what can happen (not saying it did happen here). Supplier orders a 3000-piece reel, but gets a 5000-piece reel. Supplier sells 3000 qty
in multiple cut-tape orders. Inventory system then shows zero stock. Part is marked obsolete, so no more orders. Partial reel of qty=2000 sits there
until next stocktake. Stocktake detects the partial reel, puts it aside in a discrepancy/quarantine bin. Eventually staff investigate the discrepancy.
Reel looks ok, so back it goes into a normal bin, with inventory count adjusted to 2000. Parts are now a few years old (but not eight) and
available for sale.
Another example (again, not saying it did happen). Reel goes missing: misplaced in another bin, barcode on reel doesn't read properly so reel stays
misplaced for a while. Inventory manually adjusted to zero. Part obsolete, no more orders. Reel eventually recognized as misplaced. Staff return it to
the correct bin and readjust inventory count. Parts are now a few years old and available for sale.
Apart from shelf life of electrolytics, there is the question of solderability - will the leads of the old parts solder properly, without a lot of manual touch-up?
I once worked for an OEM that would reject old parts for production, simply over that issue. It's worth asking Digi_Key about the 2013 date, if only
because of solderability concerns.