Extended Retention - keep first yearly full backup, starting 1st march

We want to keep yearly tape backups for an infinite amount of time, but the year should not start at 1st january, but 1st march. For daily, weekly and monthly I can choose, when the day, week or month is starting. But I cannot choose when the year should start.

Is this not possible? I do not want a yearly backup at the time of 1st january, but 1-2 months later. 

We also have monthly full backups, which we keep for half a year. Should I just retain one from them as infinite manually?

Thanks!