Beal seems to suggest that you might have to allege the date of the mandate in your indictment as the date finally convicted. But the concurrence seems to suggest the opposite, date of judgment is correct as long as the the mandate issued prior to date of new offense. What is everyone's take on this?

The date need not be proved as alleged in any case (no material variance will ever occur). Proof need only show finality at a pertinent point in time. Question becomes which date better notifies the Defendant of the identity of the conviction alleged. I would think most would be more likely to remember the date of sentencing in open court. They may not have any idea there was such a thing as the mandate, and certainly the date of its issuance will not be one marked in their memory. Maybe you should use the language "was convicted of ___ on ____, which conviction became final upon issuance of the mandate of the ___ Court of Appeals on ___".