Particular anniversary; in the Bible, the fiftieth
A Jubilee is often used to refer to the celebration of a particular anniversary of an event, usually denoting the 25th, 40th, 50th, 60th, and the 70th anniversary. The term comes from the Hebrew bible, initially concerning a recurring religious observance involving a set number of years, that notably involved freeing of debt slaves. Emperors of ancient Rome customarily marked anniversaries of thei... Wikipedia