[yyyy:+xx] Year Offset Suffix
Tokens > Year Tokens >
Use the Year Offset suffix to display a year that is offset by +xx years, or -xx years from the year of the current token's date.
This suffix can be added to either the [yy], [yyyy] or [year] tokens.
See also: year of now, script year, year of parent minicalendar, minical year offset modifier.