That's an interesting explanation of how it *might* have happened, Rick.. but I'm unaware of a final user ever requiring a 'date code' on such a part; the date codes are ONLY for the use of the plant making the item, for the purpose of determining problems in their production and nothing else I'm aware of.
so a plant making new items (glass or ??) in mid February, and dating it March... would seem to put it all out of whack? Now, having said that, and realizing that glass dates are ONLY for the month and year.. perhaps a week or two 'variation' doesn't really matter in glass production?
Note: On original Chevrolet cars, it is NOT unusual to see glass that varies by several months (earlier) on a car, but I personally have never seen an original glass dated AFTER a cars production. That several month variation comes not from the variation in the supplier shipments, but generally from how the assembly plant handles their incoming inventory.. (as has been said many times before, 'it ain't bread'.. and doesn't need to be rotated FIFO...)..