[yyyy:+xx] : Year Offset Suffix
Use the Year Offset suffix to display a year that is offset by +xx years, or -xx years from the value of the token that precedes it. This suffix can be added to either the [yy], [yyyy] or [year] tokens.
One special case is the :now modifier which is useful when you need to display the copyright year, regardless of the year of the diary being produced.
© Copyright [yyyy:now]
See also : Minical Year Offset Modifier and Job/Reference Number token.