I haven't heard the term before, but based on what I've found and pasted below, it's a "sliding" year as opposed to a calendar year (though "sliding year" is used in reference to astronomy).
I assume from what you posted that this would mean from Oct. 31, 2001 to Nov. 1, 2002, though it could mean from Dec. 1, 2001 to Nov. 30, 2002.
Anyway, here's an Italian explanation:

INDENNITA’ AI LAVORATORI

Il Fondo interviene con quote a favore dei lavoratori che risultano iscritti alla Lista di Mobilità regionale.

Le quote a favore dei lavoratori vengono erogate per un massimo di 16 settimane nell’arco delle ultime 52 (anno mobile), e sono indicate nelle seguenti misure.

I also found this reference from Pepsi's financial dept.

U.S. physical case volume on a constant territory basis grew a solid two percent during the fourth quarter, while international volume increased more than four percent. Worldwide physical case volume on a constant territory basis rose more than two percent for the quarter and three percent for the 52-week year. On a reported basis, worldwide physical case volume grew more than three percent for the fourth quarter and four percent for the year, excluding the impact of the 53rd week in fiscal 2000.