Duration of copyright is often based on the author's death date (see material type rules for specific information on how this works). There may be more than one author listed in a catalogue record for a work; in these cases the copyright status tool uses the latest death date or determines that the work is 'in copyright' if any of the authors are living.
Where information about life dates is missing, the copyright status tool uses risk management rules to conservatively estimate when the author would have died. If a birth date is available, but no death date, we assume that the author died by 100 years after the birth date. This means that the tool uses birth date + 100 years as the death date for purposes of copyright calculations. If no birth date is available, we use 100 years after the creation or publication date of the work as the assumed death date.