The Christian Jubilee refers to the period in time when the Christians were to be freed. They were also to be given back their land and possessions. This usually takes place after 50 years, thus it is the 50th year of independence. This is derived from the 25th chapter of Leviticus.
Leveticus 25------------- 10 And ye shall hallow the fiftieth year, and proclaim liberty throughout all the land unto all the inhabitants thereof: it shall be a jubile unto you; and ye shall return every man unto his possession, and ye shall return every man unto his family. 11 A jubile shall that fiftieth year be unto you: ye shall not sow, neither reap that which groweth of itself in it, nor gather the grapes in it of thy vine undressed. 12 For it is the jubile; it shall be holy unto you: ye shall eat the increase thereof out of the field. 13 In the year of this jubile ye shall return every man unto his possession.
In the Bible the Sabbath year occured every seven years. In Jubilee year Gods people were required to forgive all depts, free their slaves and otherwise make complete amends. The same applied to the Jubilee Sabbath year that occured every fiftieth year.