The curse of seven

Seven seems not such a lucky number for wine.

Fiona Morrison MW of Le Pin in Pomerol wrote to me at the weekend, “harvest begins week of 10 Sep – pretty depressing at the moment and it won’t be 2007 that breaks the dire pattern of ‘7 vintages since 1947.
 
"Talking to a Pomerol peasant, apparently the reason that all the years with a 7 are bad is because there are 13 moons in the year. Can any purple pagers shed further light on this?"

Any useful input below much appreciated.