Skandapurana 16.105.48

16.105.48

trayodaśa udānastu garuḍo'tha caturdaśaḥ ..
kaurmaḥ paṃcadaśo jñeyaḥ paurṇamāsī prajāpateḥ .. 48 ..

the thirteenth is Udāna, and then the fourteenth is Garuḍa;
the fifteenth should be known as Kaurma, the full-moon day of Prajāpati;