1,262. Years in Which a Leap Year May Not Be Declared

Hilchos Kiddush HaChodesh 4:14

If 30 Adar arrived without the year being declared a leap year, it should never be made a leap year because that day could be Rosh Chodesh Nisan and once Nisan begins without the year being declared a leap year, doing so is no longer possible. Nevertheless, if the court did declare a leap year on 30 Adar, the declaration is effective. If witnesses came after the leap year had already been declared and testified about seeing the moon, the court sanctifies the new month on the thirtieth day and makes it Rosh Chodesh Adar II. If they sanctified the new month on the thirtieth day before declaring a leap year, they are no longer able to declare a leap year because a leap year cannot be declared in Nisan.

Hilchos Kiddush HaChodesh 4:15

A leap year may not be declared in a year of famine when everyone is anxious to go to the storehouses for the new year’s grain. It is not permitted in such circumstances to extend the length of time that the new harvest is prohibited. We do not declare the Sabbatical year to be a leap year because everyone is permitted to take produce that grows on its own. This would make the grain necessary for the omer offering and the two loaves of bread unavailable. It was customary to declare the year before the Sabbatical year to be a leap year.