This study tackles the issue of authenticating the change of legal judgment. It puts forward a number of cases in which the legal judgment changes such as the change of the effective cause, the interest and the method of deduction. Depending on these facts, the researcher arrives at the fact that the legal judgment may change in accordance with the change of what it has been based on. This study investigates an ever-present issue of adopting astronomical calculation to determine the factual confirmation of sighting the new moon, reviews the approaches adopted by the jurisprudents and brings forward the evidence of the early jurisprudents in relying on sighting the new moon as the only method to confirm sighting the new moon.
The study also tries to collect the evidence of some early jurisprudents who hold the view of relying on astronomical calculation and tries to authenticate this view by showing its legal evidence in order to give the preponderance to the view which obligates relying on astronomical calculation.
The study concludes that the two views are not contradictory ones, yet they are like a single view but each one belongs to its own age depending on the scientific information available in that age.