The front label of the wine bottle marks the year of this wine, the year of grape means the year of harvest and brewage. It does nothing with the year of bottling.
The stand and fall of a grape year depends on the volume of rain before harvesting. If it rains a lot that year, the wine may become a bit tasteless. For example, the year 1991 and 1992, the area of Bordeaux was overcast and rainy, as a result,the grapes of 1991 and 1992 are not so sweet, the peel was thin and after brewage, the tannin contained was variously not enough and the taste was not good.
The stand and fall of a grape year also depends on the climate of spring and winter and the sunlight, etc.
There may be difference in its good or bad even in the same grape year. we should check the year table according to the district belonged. There may be difference even in the same area of the same year. For instance, 1997 is recognized as a big year for grapes, but in Bordeaux, the wine quality of MEDOC and GRAVES hypo-product area was not so good as those from POMOEWL and SAINT EMILLION hypo-product area because of a heavy rain before harvest.