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Development relies on the exquisite control of both the timing and the levels of gene expression to achieve robust developmental transitions. How cis- and trans-acting factors control both aspects simultaneously is unclear. We show that transcriptional pulses of the temporal patterning microRNA (miRNA) lin-4 are gener- ated by two nuclear hormone receptors (NHRs) in C. elegans, NHR-85 and NHR-23, whose mammalian ortho- logs, Rev-Erb and ROR, function in the circadian clock. Although Rev-Erb and ROR antagonize each other to control once-daily transcription in mammals, NHR-85/NHR-23 heterodimers bind cooperatively to lin-4 reg- ulatory elements to induce a single pulse of expression during each larval stage. Each pulse’s timing, ampli- tude, and duration are dictated by the phased expression of these NHRs and the C. elegans Period ortholog, LIN-42, that binds to and represses NHR-85. Therefore, during nematode temporal patterning, an evolu- tionary rewiring of circadian clock components couples the timing of gene expression to the control of tran- scriptional dosage.