俱舍論疏 11.85

11.85

論「增一臘縛晝夜減亦然」，答也。三十臘縛為一須臾，一百八十日增至極長。一百八十日計當六須臾，一百八十日減當六須臾。

The treatise says: "They increase by one lava; the decrease of day and night is also like this." This is the answer. Thirty lavas make one muhūrta. Over one hundred and eighty days they increase until they reach their maximum length. Over one hundred and eighty days, this amounts to six muhūrtas; over one hundred and eighty days, the decrease amounts to six muhūrtas.