Human slavery takes many forms.
In its most literal sense slavery refers to economic servitude to an exploiting master. But a man can be a slave to time, to creativity and to passion. While literal slavery is virtually a thing of the past, these extended forms of slavery have always been and still are very much a part of the human condition. It was G-d's special gift to His beloved people to provide them with three mitzvot that would liberate them from such enslavement. This was a directive to the Sanhedrin the Torah leadership of the nation to determine the calendar of the celebration of all holidays and festivals based on their astronomic calculations and the testimony of witnesses who had sighted the new moon.