1,259. How the Leap Year was Declared

Hilchos Kiddush HaChodesh 4:8

Taking these other things into account means that the court says that a leap year must be declared because the equinox falls late, or the barley has not yet ripened and the fruit trees have not yet blossomed, plus the young goats are too small and the doves are not yet mature.

Hilchos Kiddush HaChodesh 4:9

A leap year can only be declared by judges. The head of the High Court tells some other members to convene at a given place to make calculations and to deliberate regarding the necessity to declare a leap year. Only those who were invited are empowered to declare a leap year. They start with three ordained judges from the Sanhedrin. If two of them say that there is no need to discuss the matter, we follow their opinion even if the third judge thinks they should continue. If two judges say they need to continue deliberating the need for a leap year and the third judge disagrees, two more judges who had been invited previously are added and the discussion continues.