The 'Year of Death' fields allow you to narrow your search to a specific time period. You can enter a 'From' year, a 'To' year, or both. For example, to search for someone who died between 1990 and 2000, you would enter '1990' in the 'From' field and '2000' in the 'To' field. If you only know the exact year of death, you can enter it in both fields.