Maitri (Maitrāyaṇīya) Upaniṣad 6.15

6.15

dve vāva brahmaṇo rupe kālaścākālaścātha yaḥ prāgādityātso'kālo'kālo'tha ya ādityadyaḥ sa kālaḥ sakalaḥ sakalasya vā etadrūpaṃ yatsaṃvatsaraḥ saṃvatsarātkhalvevemāḥ prajāḥ prajāyante saṃvatsareṇeha vai jātā vivardhante saṃvatsare pratyastaṃ yanti tasmātsaṃvatsaro vai prajāpatiḥ kālo'nnaṃ brahmanīḍamātmā cetyevaṃ hyāha
kālaḥ pacati bhūtāni sarvāṇyeva mahātmani |
yasmin tu pacyate kālo yastaṃ veda sa vedavit ||

15. There are, assuredly, two forms of Brahma: Time and the Timeless. That which is prior to the sun is the Timeless (a-kāla), without parts (a-kala). But that which begins with the sun is Time, which has parts. Verily, the form of that which has parts is the year. From the year, in truth, are these creatures produced. Through the year, verily, after having been produced, do they grow. In the year they disappear. Therefore, the year, verily, is Prajāpati, is Time, is food, is the Brahma-abode, and is Ātman. For thus has it been said:—

'Tis Time that cooks created things,
All things, indeed, in the Great Soul (mahātman).
In what, however, Time is cooked—
Who knows that, he the Veda knows!