When looking at the list of 1SE backups you can restore from, this is what's available for you:
The five most recent backups;
concerning the fifth most recent backup, all backups on the same or prior day;
the most recent backup per day for the previous seven days;
the most recent backup per week for the previous three weeks;
the most recent backup per month for the previous three months.
If you made a backup last year and haven't done any since, that old backup remains. However, once you create a new backup, the older one is marked for deletion. Therefore, if new backups have been made recently, you cannot restore a backup from a year ago.
Intended to merge your old backup with new content?