As for that night, let darkness seize upon it; let it not be joined unto the days of the year, let it not come into the number of the months.

Let a darksome whirlwind seize upon that night, let it not be counted in the days of the year, nor numbered in the months.

That night let gloom seize upon it; let it not rejoice among the days of the year; let it not come into the number of the months.

That night, let thick darkness take it, Let it not be united to days of the year, Into the number of months let it not come.

That night--let the thick dark take it; let it not have joy among the days of the year; let it not come into the number of the months.

Let a whirlwind of darkness take hold of that night, let it not be counted in the days of the year, nor numbered in the months.

As for "that night." Job, having cursed the day, proceeds to utter a malediction on the "night" also; see Job 3:3. This malediction extends to Job 3:9.
Let darkness seize upon it - Hebrew, Let it take it. Let deep and horrid darkness seize it as its own. Let no star arise upon it; let it be unbroken and uninterrupted gloom. The word "darkness," however, does not quite express the force of the original. The word used here אפל 'ôphel is poetic, and denotes darkness more intense than is denoted by the word which is usually rendered "darkness" השׁך chôshek. It is a darkness accompanied with clouds and with a tempest. Herder understands it as meaning, that darkness should seize upon that night and bear it away, so that it should not be joined to the months of the year. So the Chaldee. But the true sense is, that Job wished so deep darkness to possess it, that no star would rise upon it; no light whatever be seen. A night like this Seneca beautifully describes in Agamemnon, verses 465ff:
Nox prima coeltum sparserat stellis,
Cum subito luna conditur, stellae cadunt;
In astra pontus tollitur, et coelum petit.
Nec una nox est, densa tenebras obruit
Caligo, et Omni luce subducta, fretum
Coelumque miscet
Premunt tenebrae lumina, et dirae stygis
Inferna nox est.
Let it not be joined unto the days of the year - Margin, "rejoice among." So Good and Noyes render it. The word used here יחד yı̂chad, according to the present pointing, is the apocopated future of חדה chādâh, "to rejoice, to be glad." If the pointing were different יחד yâchad it would be the future of יחד yachad, to be one; to be united, or joined to. The Masoretic points are of no authority, and the interpretation which supposes that the word means here to exult or rejoice, is more poetical and beautiful. It is then a representation of the days of the year as rejoicing together, and a wish is expressed that "that" night might never be allowed to partake of the general joy while the months rolled around. In this interpretation Rosenmuller and Gesenius concur. Dodwell supposes that there is an allusion to a custom among the ancients, by which inauspicious days were stricken from the calendar, and their place supplied by intercalary days. But there is no evidence of the existence of snell a custom in the time of Job.
Let it not come etc - Let it never be reckoned among the days which go to make up the number of the months. Let there be always a blank there; let its place always be lacking.

As for that night, let darkness seize upon it - I think the Targum has hit the sense of this whole verse: "Let darkness seize upon that night; let it not be reckoned among the annual festivals; in the number of the months of the calendar let it not be computed." Some understand the word אפל ophel as signifying a dark storm; hence the Vulgate, tenebrosus turbo, "a dark whirlwind." And hence Coverdale, Let the darck storme overcome that night, let it not be reckoned amonge the dayes off the yeare, nor counted in the monethes. Every thing is here personified; day, night, darkness, shadow of death, cloud, etc.; and the same idea of the total extinction of that portion of time, or its being rendered ominous and portentous, is pursued through all these verses, from the third to the ninth, inclusive. The imagery is diversified, the expressions varied, but the idea is the same.

As for that night,.... The night of conception; Job imprecated evils on the day he was born, now on the night he was conceived in, the returns of it:
let darkness seize upon it; let it not only he deprived of the light of the moon and stars, but let an horrible darkness seize upon it, that it may be an uncommon and a terrible one:
let it not be joined unto the days of the year; the solar year, and make one of them; or, "let it not be one among them" (c), let it come into no account, and when it is sought for, let it not appear, but be found wanting; "or let it not joy" or "rejoice among the days of the year" (d), as Jarchi, Aben Ezra, and others interpret it, or be a joyful one, or anything joyful done or enjoyed in it:
let it not come into the number of the months; meaning not the intercalated months, as Sephorno, nor the feasts of the new moon, as others, but let it not serve to make up a month, which consists of so many days and nights, according to the course of the moon; the sense both of this and the former clause is, let it be struck out of the calendar.
(c) "non sit una inter dies", Pagninus; "ne adunatur in diebus", Montanus. (d) "Ne fuisset gavisa", Junius & Tremellius; "ne gaudeat", Vatablus, Beza, Mercerus, Piscator, Drusius, Broughton, Cocceius, Schmidt, Schultens, Michaelis.

seize upon it--as its prey, that is, utterly dissolve it.
joined unto the days of the year--rather, by poetic personification, "Let it not rejoice in the circle of days and nights and months, which form the circle of years."

6 That night! let darkness seize upon it;
Let it not rejoice among the days of the year;
Let it not come into the number of the month.
7 Lo! let that night become barren;
Let no sound of gladness come to it.
8 Let those who curse the day curse it,
Who are skilled in stirring up leviathan.
9 Let the stars of its early twilight be darkened;
Let it long for light and there be none;
And let it not refresh itself with eyelids of the dawn.
Darkness is so to seize it, and so completely swallow it up, that it shall not be possible for it to pass into the light of day. It is not to become a day, to be reckoned as belonging to the days of the year and rejoice in the light thereof. יחדּ, for יחדּ, fut. Kal from חדה (Exodus 18:9), with Dagesh lene retained, and a helping Pathach (vid., Ges. 75, rem. 3, d); the reverse of the passage Genesis 49:6, where יחד, from יחד, uniat se, is found. It is to become barren, גּלמוּד, so that no human being shall ever be conceived and born, and greeted joyfully in it.
(Note: Fries understands רננה, song of the spheres (concentum coeli, Job 38:37, Vulg.); but this Hellenic conception is without support in holy Scripture.)
"Those who curse days" are magicians who know how to change days into dies infausti by their incantations. According to vulgar superstition, from which the imagery of Job 3:8 is borrowed, there was a special art of exciting the dragon, which is the enemy of sun and moon, against them both, so that, by its devouring them, total darkness prevails. The dragon is called in Hindu râhu; the Chinese, and also the natives of Algeria, even at the present day make a wild tumult with drums and copper vessels when an eclipse of the sun or moon occurs, until the dragon will release his prey.
(Note: On the dragon rhu, that swallows up sun and moon, vid., Pott, in the Hallische Lit. Zeitschr. 1849, No. 199; on the custom of the Chinese, Kuffer, Das chinesische Volk, S. 123. A similar custom among the natives of Algeria I have read of in a newspaper (1856). Moreover, the clouds which conceal the sky the Indians represent as a serpent. It is ahi, the cloud-serpent, which Indra chases away when he divides the clouds with his lightning. Vid., Westergaard in Weber's Indischer Zeitschr. 1855, S. 417.)
Job wishes that this monster may swallow up the sun of his birth-day. If the night in which he was conceived or born is to become day, then let the stars of its twilight (i.e., the stars which, as messengers of the morning, twinkle through the twilight of dawn) become dark. It is to remain for ever dark, never behold with delight the eyelids of the dawn. בּ ראה, to regale one's self with the sight of anything, refresh one's self. When the first rays of morning shoot up in the eastern sky, then the dawn raises its eyelids; they are in Sophocles's Antigone, 103, χρυσέης ἡμέρας βλέφαρον, the eyelid of the golden day, and therefore of the sun, the great eye.

Darkness - Constant and extraordinary darkness, without the least glimmering of light from the moon or stars. Be joined - Reckoned as one, or a part of one of them.