:year+YY or :year-YY
where the black text (:year+ and :year-) are to be be used literally, and the YY represents the numerical offset running from 1 to 99.
The current script year can be specified with the modifier :year+0 but it can also be specified more simply as :year where the +0 is omitted.
For example, in the example below we want to have 13 minicalendars at the bottom of every page, showing the months from July of the year before the Script year to July of the year of the script, and we want these minicalendars to always show these months, regardless of the dates of the current page/spread.
See also: Minicalendar Starting Date Offset Modifier, Minicalendar Current Week Offset Modifier, Minicalendar Year Offset Modifier, Date Offset Suffixes, [year] : Script Year, [yyyy:now] : Year of Now,