In a Hebrew leap year, an extra month, referred to as Adar II, is added to the calendar. In ancient times, a leap year was declared if the Hebrew month of Nisan, when Passover takes place, would deviate too far from the spring equinox, if the barley crops were ripening late or if the fruit trees were not blossoming yet. Other issues, such as infrastructure work needed before the pilgrimage to Jerusalem or travel issues affecting the pilgrimage, could also warrant a leap year. Eventually, the Hebrew calendar was calculated and fixed by Hillel, a 4th century Jewish scholar, through mathematical calculations and the courts ceased to declare and calculate new months.
Yedidiah Efraim Meshulami made the request for a Hebrew leap year because of what he called the "side effects" of the coronavirus outbreak. Many Jews fear that the Passover seder this year will take place during a lock down situation and it may be more difficult to obtain the necessary food and supplies for the seder. Meshulami believed that a leap year declaration could help avoid that situation, according to Calcalist.
The Supreme Court denied the request, saying that there is no legal mechanism for declaring a leap year due to an emergency and that the court was not at the level of the Sanhedrin, the highest level court in Jewish law, and therefore did not have the authority to make such a decision.
According to Jewish law, decisions on the calendar can only be made by rabbis who have "semicha," authority granted to them by another rabbi who received authority from another in a chain reaching back to Moses, according to Maimonidies. The chain was broken sometime after the destruction of the Second Temple in Jerusalem, meaning that rabbis today may not have the authority to make such decisions.
The Supreme Court noted it seemed to them that, even according to Jewish religious law, the claims of the petitioner had no basis.