Quatrain 31

Ah, but my Computation, People say,
Reduced the Year to better Reckoning?
Nay,
'Twas only striking from the Calendar
Unborn To-morrow, and dead Yesterday.

FitzGerald, Stanza LVII, 4th ed.

FitzGerald's forerunner, Stanza XXXVII of the  first edition, 1859:

Ah,  fill the cup:—what boots it to repeat
How Time is slipping underneath our Feet:
Unborn TO-MORROW, and dead YESTERDAY,
Why fret about them if TO-DAY be sweet?

There is a quatrain below that may have some bearing on FG's 4th edition rendition.  This poem is found in Dashti (70), Forughi (129), Whinfield (350), and Saidi (47).  Heron-Allen, p. 89, records it as inspiration for FitzGerald's stanza LVII.  According to H-A, it appears in the Calcutta MS, 381:

دشمن به غلط گفت که من فلسفیم 
ایزد داند که آنچه او گفت نیم
لکین چو  درین غم‌آشیان آمده‌ام
آخر کم از آن که من بدانم که کیم

Dashti 70, p. 256

H-A's text the same except for ندانم in the final line as does Whinfield's 350. The texts of Forughi 129 and Saidi 47 concur with Dashti's reading.

doshman be ghalat goft ke man falsafiyam
izad daanad ke aanche u goft nayam
likan cho dar in ghamaashyaan aamadeam
aakhar kam az aan ke man bedaanam ke kiyam

Philosopher? Enemies are wrong to call me that.
God knows I am not what they say I am.
Yet since I have come to stay in this sad dwelling,

of this— just who I am— I know nothing at all.

In a footnote to this quatrain, Ali Dashti conjectures that Khayyaam may be playing it safe by calling attention to his non-attachment to philosophy.  As we have seen, boldness serves him well if it can be interpreted "mystically", e.g., the consumption of wine.  In this case, philosophy and religion do not go hand in hand, and there is no mystic solution.

The translation or understanding of the quatrain caused two problems: the first is easy enough-- ghamaashyaan is a compound noun "nest of grief/sadness".  The fourth line I am not sure of but think that he is saying he knows next to nothing about who he is: kam az aan ke man bedaanam means in my opinion, " I know scarely anything." This is khayyaamic (as Dashti points out) and further separates him from the "philosopher" he does not wish to claim to be.  Is it possible that the speaker leaves himself open to guidance in his not-knowing?  A safe ploy in this quatrain?

There is another quatrain from the Bodleian collection, MS 20, which seems to supply the last two lines of FitzGerald's rendition and has doubtless influenced the 1st edition Stanza.

چون آب به جویبار و چون باد بدشت
روزی دگر از نوبت عمرم بگذشت
هرگز غم دو روز مرا یاد نگشت
روزی که نیامدست و روزی* که گذست

chon aab bejuybaar o chon baad bedasht
ruzi degar az nowbat-e ‘omram begozasht
hargez gham-e do ruz maraa yaad nagasht
ruzi ke nayaamadast o ruzi * ke gozasht

* I haven't seen the MS but it is transcribed روز which isn't metrically correct.  Arberry, Romance ... 214 has made this correction in his transcription.  Arberry also calls attention to this quatrain's inclusion in the Calcutta MS (#22) with a slightly different text.  

These days hurry on— 
time and life have passed
the flow of water in rivers
or winds across the plain ...
two days never to sorrow over
(let them cling to my thoughts):
the day that's not here
the day that is past.

 

The Latin 'sketch':
Velut Aura per Desertum, velut unda Rivulorum
Nostrae Vitae Dies alter evolavit deditorum;
At duorum me Dierum [...]
Scilicet non adhuc venti, scilicet praeteriti.

Like the wind through the desert, like water in streams
another day given us in our life has flown away;
Yet two days [do not concern] me:
that's the day not yet come and the day gone by.

FitzGerald gets to the heart of carpe diem in his last two lines as does his source.  Although he has no note on the first two lines in his editions, he obviously refers to Khayyaam's part in calendar reform (the taqvim-e jalali in 1079 C.E.), where the "better Reckoning" proved to be just that: a calendar that was one day short every 5,000 years rather than every 3,000 years as  in the Gregorian calendar.  The account of Khayyaam's work on the calendar as a member of a commission established by Sultan Jalal al-Din Malik Shah is well-known, but Robert Irwin in his review of Mehdi Aminrazavi's Wine of Wisdom casts doubts: "there is no direct evidence that Khayyam was involved in the reform of the Persian calendar ... as Aminrazavi [28-29; 199-200] and many before him have suggested. (The view that he did is based on the careless reading of a thirteenth-century Arab chronicler.)" Robert Irwin, Times Literary Supplement, December, 23 & 30, 2005, p. 10-11.