Jaiminīya (Talavakāra) Brāhmaṇa 2-7.226.p4

2-7.226.p4

tadyattrivṛtassataścaturviṃśaṃ bahiṣpavamānaṃ bhavati caturviṃśatyardhamāsassaṃvatsaraḥ

In that the bahiṣpavamāna is twenty-four-fold, being [normally] nine-fold—the year consists of twenty-four half-months;