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A jubilee is a particular anniversary of an event, usually denoting the 25th, 40th, 50th, 60th, and the 70th anniversary. The term is often now used to denote the celebrations associated with the reign of a monarch after a milestone number of years have passed.
The Jubilee (Hebrew: יובל yovel) year (every 50th year) and the Sabbatical year (every seventh year) are Biblical commandments concerning ownership of land and slaves. The laws concerning the Sabbatical year are still observed by many religious Jews in the State of Israel, while the Jubilee has not been observed for many centuries. According to the Hebrew Bible, every seventh year, farmers in the land of Israel are commanded to let their land lie fallow, and slaves were freed. The celebration of the Jubilee is the fiftieth year, that is, the year after seven Sabbatical cycles.
These are also used as general terms in the modern world.