I always use Mr. Malty's Pitching Rate Calculator before I brew to make an appropriate starter. The viability of White Labs vials are based on the date 4 months prior to the best buy date. I just got three vials with May 6 2011 best buy dates. That puts the production date at 1/6/2011. Today is 1/5/2011, do I still use 1/6/2011 as the production date?