The methods are as follows: - gets the era object for the next era. Returns if it doesn't exist. - gets the era object for the previous era. Returns if it doesn't exist. - gets the era object for the "old" era. This is the same as the current era object unless eraYear equals 1. If eraYear equals 1 then this returns the era object for the previous era. If the module could not find a valid previous era object then the current era object is returned.