Leviticus 25:8 "And you shall count seven Sabbatical years"

The Shemitah and Yovel cycle are very significant, each one setting specific times and dates for the many obligations that must be fulfilled accordingly.

Can you imagine different people keeping separate calendars and timetables?

In order to assure a calendar that would apply universally, the Beit-Din of the Great Sanhedrin (Assembly) are commanded to calculate the cycles providing the public with a fixed calendar for Shemitah and Yovel.