וספרת לך שבע שבתת שנים שבע שנים שבע פעמים והיו לך ימי שבע שבתת השנים תשע וארבעים שנה והעברת שופר תרועה בחדש השבעי בעשור לחדש ביום הכפרים תעבירו שופר בכל ארצכם וקדשתם את שנת החמשים שנה וקראתם דרור בארץ לכל ישביה יובל הוא תהיה לכם ושבתם איש אל אחזתו ואיש אל משפחתו תשבו (ויקרא כה, ח-י)
The Counting
The Torah commands to count a cycle of 7 years (Shmitah) and 7 sets of 7 years (Yovel). The laws of Yovel are the same as the laws of the years of Shmitah regarding the prohibition to work the land of Israel. The additional laws of Yovel also involve the freeing of slaves and the returning of sold ancestral lands.
The Gemara (Arachim 12b-13a, Nedarim 61a) records a dispute in understanding the count of years of Shmitah and Yovel. According to the Chachumim the Yovel immediately follows the 49th year and that year does not count towards the counting of the next Shmitah cycle. Rabbi Yehudah says the Yovel year also counts as the first year of the Shmitah cycle.
Thus, according to the Chachumim the Yovel occurs every 50 years. According to Rabbi Yehudah the Yovel occurs every 49 years (after the first set). According to both opinions the Yovel is anchored to occur the year after the 7th Shmitah year.
Third Opinion:
Rabbi Yehudah in Yerushalmi Kedushin 1:2 is an understanding of Rabbi Yehudah that agrees the Yovel occurs every 50 years, but the first year of the new Shmitah cycle occurs the year after the completion of the 49 years (7 cycles of 7 years). Thus, the Yovel which occurs every 50 years can occur in any year of the Shmitah cycle and is not anchored to the 7th Shmita year.
