The adjective halcyon is hard to use outside of the phrase halcyon days, and the reason has to do with its origin and development.
A halcyon is a sort of bird which we nowadays call a kingfisher.¹ The halcyon was supposed to have built a nest on or near the sea, and to have incubated her eggs during the relatively peaceful weather surrounding the winter solstice.
The Greeks explained this midwinter period of calm by saying that the body of Ceyx, a young demigod, floated to shore after his ship was destroyed in a midwinter storm. He was found by his lover, Alcyone, daughter of Aeolus, the god of winds. Overwhelmed by grief, she drowned herself in the sea. The gods took pity on the couple and reunited them, transforming them into kingfishers. Aeolus quieted the winds every year to protect his daughter’s nest.²
So, since antiquity, the phrase halcyon days has literally meant this nesting period of about two weeks of calm weather surrounding the winter solstice.³ The phrase has also come to be used as a metaphor meaning any calm, peaceful, or fruitful moment between difficulties. And out of it, in a sort of back formation, halcyon has transformed again, this time from a bird (a noun adjunct in the phrase halcyon days) into a separable adjective meaning “calm” or “peaceful”. But the transformation is incomplete. Halcyon (adj.) still pairs mostly with words for time or space: for example, “days”, “years”, “air”, or “atmosphere”.⁴
Poetically speaking, the affinity between halcyon and time and space words is apt because of Ceyx’s family connections. The travels of his father Eosphorus through space marked the passage of time and the seasons. Eosphorus was the “dawnbringer”, “lightbringer”, or “daystar”, known today as Venus rising. His particular brightness before sunrise during the halcyon days presaged the weakening of winter and the return of longer days and fruitful weather.⁵