Śatapatha Brāhmaṇa ("of a hundred paths") 3.4.4.16

3.4.4.16

saṃvatsaro vajraḥ | etena vai devāḥ saṃvatsareṇa vajreṇa puraḥ prābhindannimāṃlokānprājayaṃstatho evaiṣa etena saṃvatsareṇa vajreṇemāṃlokānprabhinattīmāṃlokānprajayati tasmādetā devatā yajati

The thunderbolt is the year: by that year, as a thunderbolt, the gods clove the strongholds and conquered these worlds. And so does he now by that year, as a thunderbolt, cleave these worlds, and conquer these worlds. This is why he offers to those gods.