Art is timeless, its beauty as immutable as the North Star. Timelessness can also come from people not having a clue when something was created. Knowing the year of its inception is one thing, as historians can guess at the fashions and trends of the artist’s era, but creative types, like poets, are also moved by the seasons.
Sappho of Eresos would be no different than our contemporaries. Rivalling Homer in her stature, and celebrated for her lyrical and lucid style, only fragments of her writing survive in the 21st century. Among Sappho’s oeuvre is her Midnight Poem:
The moon has set
And the Pleiades;
It is midnight,
The time is going by,
And I sleep alone.
Bringing us to an astronomical analysis of her poem by Manfred Cuntz (ahem) and his associate Levent Gurdemir. Using a program called Starry Night, they were able to estimate the date Sappho wrote her wistful words. Playing around with their programs, the team deduced Sappho put stylus to tablet sometime between January 25th and March 31st in 570 B.C.E.. 
Had she meant to convey the time and date by noting the moon and the Pleiades set together, then the moon would’ve been at its first quarter.  Poking around with Stellarium, a free, multi-platform planetarium program, I’d gather the date was Tuesday the 1st of February 570 B.C.E..
While a hopeless romantic, Sappho’s poem may have been a wish for extra warmth rather than some nudge-nudge wink-wink say-no-more.
Scientists use planetarium’s advanced astronomical software to accurately date 2,500 year-old lyric poem – http://phys.org/news/2016-05-scientists-planetarium-advanced-astronomical-software.html
The Phases of the Moon – http://www.astro.cornell.edu/academics/courses/astro201/moon_phase_pict.htm
Moon Phases – Rising & Setting Times – http://www.wsanford.com/~wsanford/exo/moonrise-set.html