These two wonderful lines in an 85-line odd poem of unknown authorship written between the 1st and 4th centuries have drawn translators from Thomas Parnell to Ezra Pound to Allen Tate to any number of university professors:
Cras amet qui nunquam amati
Quique amavit tras ame.
They seemed plain enough when I first read them: and so “Let whoever has not loved, love tomorrow / Whoever has loved, love tomorrow,” was my translation. Others came up with versions that seem, well, quirky: Allen Tate’s Tomorrow may loveless, may lover tomorrow make love seems quirkiest, being so nearly incomprehensible, but close in the running is also Now learn ye to love who loved never—now ye who have loved, love anew! by Arthur Quiller-Couch or Let the loveless love tomorrow, let the lover love again, by J. F. Pobson, M.A., a professor of Greek in the University of Bristol Cambridge. Tate’s oddness seemed confusing for such an otherwise terrific poet. Here is his explanation, which I read as him trying to stuff a little too much baggage into his version:
In the fall of 1942 the refrain of the Pervigilium came back to me and for several days kept running through my head; then I suddenly knew that I ‘had’ it. I had it, that is to say, in language that somewhat resembled English and in a metre that the English language can be written in: plain iambic pentametre, with anapaestic substitutions for the frequent falling rhythms of the original. The Latin is in trochaic septenarii, seven-footed lines with, at the end, an extra syllable which is usually accented, making eight accents; the metre, in fact, of Tennyson’s Locksley Hall, which was actually used by some of the early translators of the Pervigilium. Except for certain special purposes it is an impossible metre in English, for unless the extra accented syllable at the end is managed with great skill the line will break down into units of four and three and sound like a Wesleyan hymn—a high price to pay for metrical fidelity to a foreign original.
Jeepers. On the bright side, the explanation shows that there is room in the world of translating for many versions, born of many different considerations. Some translators strive for word-perfect and even scansion or rhyme-perfect versions; these can be admirable, but to my ear too many are like Samuel Johnson’s description of a dog walking on his hind legs: “It is not done well; but you are surprised to find it done at all.” Here are others, more than a few at least as quirky as Tate:
Let whoever never loved, love tomorrow,
Let whoever has loved, love tomorrow.
— Ezra Pound
Let those love now, who never loved before,
Let those who always loved, now love the more.
— Thomas Parnell
Tomorrow may loveless, may lover tomorrow make love.
— Allen Tate
He that never loved before,
Let him love to-morrow!
He that hath loved o’er and o’er,
Let him love to-morrow!
— Unknown, Blackwood magazine, June, 1843.,Vol. LIII
Now learn ye to love who loved never—now ye who have loved, love anew!
— Arthur Quiller-Couch
Let the loveless love tomorrow, let the lover love again,
— J. F. Pobson, M.A.,
Professor of Greek in the University of Bristol Cambridge
Everyone tries because the originals are so wonderful, and thus tempting, and not just for poets. Those two lines sent Walter Pater into a sugary overload of many pages in his Marius the Epicurean. Here is a sample:
…It was one of the first hot days of March—”the sacred day”—on which, from Pisa, as from  many another harbour on the Mediterranean, the Ship of Isis went to sea, and every one walked down to the shore-side to witness the freighting of the vessel, its launching and final abandonment among the waves, as an object really devoted to the Great Goddess, that new rival, or “double,” of ancient Venus, and like her a favourite patroness of sailors. On the evening next before, all the world had been abroad to view the illumination of the river; the stately lines of building being wreathed with hundreds of many-coloured lamps. The young men had poured forth their chorus—
Cras amet qui nunquam amavit,
Quique amavit cras amet—
as they bore their torches through the yielding crowd, or rowed their lanterned boats up and down the stream, till far into the night, when heavy rain-drops had driven the last lingerers home. Morning broke, however, smiling and serene; and the long procession started betimes. The river, curving slightly, with the smoothly paved streets on either side, between its low marble parapet and the fair dwelling-houses, formed the main highway of the city; and the pageant, accompanied throughout by innumerable lanterns and wax tapers, took its course up one of these streets, crossing the water by a bridge up-stream, and down the other, to the haven, every possible standing-place, out of doors and within, being crowded with sight-seers, of whom Marius was one of the most eager, deeply interested in finding the spectacle much as Apuleius had described it in his famous book….
In the expression of all this Flavian seemed, while making it his chief aim to retain the opulent, many-syllabled vocabulary of the Latin genius, at some points even to have advanced beyond it, in anticipation of wholly new laws of  taste as regards sound, a new range of sound itself. The peculiar resultant note, associating itself with certain other experiences of his, was to Marius like the foretaste of an entirely novel world of poetic beauty to come. Flavian had caught, indeed, something of the rhyming cadence, the sonorous organ-music of the medieval Latin, and therewithal something of its unction and mysticity of spirit. There was in his work, along with the last splendour of the classical language, a touch, almost prophetic, of that transformed life it was to have in the rhyming middle age, just about to dawn. The impression thus forced upon Marius connected itself with a feeling, the exact inverse of that, known to every one, which seems to say, You have been just here, just thus, before!—a feeling, in his case, not reminiscent but prescient of the future, which passed over him afterwards many times, as he came across certain places and people. It was as if he detected there the process of actual change to a wholly undreamed-of and renewed condition of human body and soul: as if he saw the heavy yet decrepit old Roman architecture about him, rebuilding on an intrinsically better pattern. Could it have been actually on a new musical instrument that Flavian had first heard the novel accents of his verse? And still Marius noticed there, amid all its richness of expression and imagery, that firmness of outline he had always relished so much in the composition of  Flavian. Yes! a firmness like that of some master of noble metal-work, manipulating tenacious bronze or gold. Even now that haunting refrain, with its impromptu variations, from the throats of those strong young men, came floating through the window.
Cras amet qui nunquam amavit,
Quique amavit cras amet!
—repeated Flavian, tremulously, dictating yet one stanza more.
Here is some background on the poem: The authorship is anonymous, and the dating uncertain, meaning that no one is sure who wrote it, or exactly when. Some scholars believe it to have been written in the reign of Hadrian (A.D. 117–138) by Publius Annius Florus, who was better known as an historian and rhetorician than as a poet. This dating is somewhat wishful, as it relies on when the poem should have been written, because under Hadrian the spring ritual of the Greek cult of Venus Genetrix, whom the poem celebrates as the principle of sexual reproduction in nature, was officially encouraged and given the dignity of a state religion. (The feast survives today as May Day.) Others see some stylistic features of the poem as similar to poems written later, such as the Eclogues of Nemesianus of Carthage (circa A.D. 285), or fragments of Tiberianus, whose “Amnis Ibat” (around A.D. 350) has a similar but not identical meter and whose subjects are the natural world and the “Pleasant Place.” The scansion of his poem and Pervigilium is unusual, a trochaic tetrameter, much like Tennyson’s “Locksley Hall” (Comrades, leave me here a little, while as yet ‘t is early morn: // Leave me here, and when you want me, sound upon the bugle-horn), rather than the quantitative arrangement of long and short syllables favored by most Latin poetry at the time. This point was also made by Alan Tate in his introduction to his translation. Others have noted that this change in metric is historic, signaling a change in sensibility so great as to be the pivot point at which Latin poetry began its change to medieval.
The poem has survived in two MSS., both corrupt, both perhaps the work of (as one critic says) “two illiterate copyists who—strange to say—were both smatterers enough to betray their little knowledge by converting Pervigilium into Per Virgilium (scilicet, by Virgil’): thus helping us to follow the process of thought by which the Middle Ages turned Virgil into a wizard.” The result of the differences in the poem’s ordering has been a lot of guesswork as to the right arrangement.
The poem consists of ninety-three verses in trochaic tetrameter, divided into stanzas of unequal length by the refrain Cras amet qui nunquam amavit, / Quique amavit cras amet. The time of the poem is early spring on the eve of a three-night festival of Venus (April 1–3) in what seems to be Sicily, and it describes the annual awakening of the vegetable and animal world through the intercession of Venus. This awakening contrasts with the isolation and loneliness of the speaker. This focus on the natural world in opposition to the corrupt world of the city is also marks a new note in Roman poetry, and is seen by some critics as more evidence of the beginning of the transition from Roman to medieval poetry.
I have taken some liberties with the structure and arrangement of the work, dropping the goddess superstructure of the work and retaining the spring and the joy. I have shortened the stanzas, keeping as much as it seems to me moves the poem forward, and focused the result on the refrain. I take as my aesthetic here a notion that maybe our duty as translators is to deliver not so much a word-perfect result as a poem-perfect one, that sounds similar bells and evokes similar responses in the new culture and new language. That may make the result less a translation than an imitation. A great translation can be a great new poem—think of Pound’s Cathay, or Rosetti’s translations of Villon (“But where are the snows of yesteryear?”), or Robert Bly’s versions of Neruda. I don’t claim such greatness for this translation, only greater readability compared to some of the other translations.
Spring, & the goddess, a clear sound from the waves;
& in the groves & hollows, the mating rains,
& in the small houses of the leaves:
Let whoever who has not loved, love tomorrow,
Whoever has loved, love tomorrow
& the blood rising & the ocean foam,
Horses & sand, violence of horses
When the goddess arrives, wave-born in the mating rain:
Let all who have not loved, love tomorrow,
& all who have loved, love tomorrow
For the year’s been like death; & now there are flowers.
For the year’s been still & gray; & now there is wind.
How the dew is scattered & the night wind calls,
How the tears about to fall
Are held, & the blush begins.
Now the stars rain down on cloudless nights,
& the stiff gestures of married women grow soft.
The rose is wed to the dew, & the pale dresses
Of flowers open softly at morning, to ocean gems
& flames, & to the purple of first light,
Past responsibilities, past care, all
But Love’s kisses & the rising blood:
Let any who have not loved, love tomorrow,
& any who have loved, love tomorrow.
Now the young girl approaches her father
That his strictness might waver,
& the young man at the front door does not hesitate,
& in the grove, the chorus sings,
& in the field there is constant song.
Let whoever has not loved, love tomorrow
& whoever has loved, love tomorrow
& the goddess rules & gives commands,
That the flower shall be spent in the forest,
That no wild thing come forth but shall be loved,
& the women seek their lovers, in her honor;
Listen, for the swans grow hoarse in the streams,
& the animals are gentle, with gentle songs.
The birds break their winter silence, & the rains begin.
Yet there is one song a young girl sings.
& sings so beautifully,
That love seems the reason, not sorrow…
So the tradesman stops in the forest, & is silent,
& puts down his tools, & is silent;
& listens as she sings so beautifully
To no one & to everyone,
When shall my own spring come,
& my silence end?
Let whoever has not loved, love tomorrow
& whoever has loved, love tomorrow.