करोत्येकमहश्छेदं तथैवैकं च चन्द्रमाः ॥ कZ_०२.२०.६५च्द् ॥
karoty ekam ahaś-chedaṃ tathaiva ekaṃ ca candramāḥ
So bewirkt es (im Laufe der Zeit) eine Kürzung/Anpassung um einen Tag; ebenso bewirkt auch der Mond eine (Anpassung um einen Tag).
A formal rule for inserting/removing days to keep the official calendar aligned with observable cycles, preventing administrative disorder.