The vintage of a wine is all about the year the grapes were harvested. In Europe and America, the fruit will have blossomed and ripened in the same calendar year. In New Zealand, where the spring and summer span a date change, the vintage refers specifically to the year in which the grapes were picked.

The convention is that the vintage printed on the bottle will refer to the year that the majority of the fruit used in making that wine was picked. If you buy a wine that has no vintage, it will be a blend of wines from across several different years.

Knowing the vintage of a wine is important to get the cellaring time right. Not all wines cellar well. Sauvignon Blanc, for example, is a 'drink-now' wine, enjoying up to 24 months unopened. Gewurztraminer and Pinot Gris like to be opened after three to four years, while Riesling, oaked Chardonnay, and Syrah would probably benefit from five. A top-quality Pinot Noir or a good dessert wine will age nicely beyond five years. Cabernet dominant ‘Bordeux style’ wines improve over periods of decades. 

The cellaring time is always from the year of harvest, not the year of purchase; and the more expensive the wine, the more likely it will enjoy sitting around.

Another good reason to know the vintage is because some years are better than others. For example, 1998 was an excellent year for Hawke's Bay Cabernet and Merlot, while 2010 was a good year for Canterbury Pinot Noir; both are ready to enjoy now. Whether you are buying wine to cellar as an investment, or to impress your dinner guests tonight, do a little bit of research on good years before you pull out your EFTPOS card.