They change - The word "they" in this place, some understand as referring to his friends; others, to his thoughts. Rosenmuller supposes it is to be taken impersonally, and that the meaning is, "night is become day to me." Wemyss translates it, "night is assigned me for day." So Dr. Good renders it. The meaning may be, that the night was to him as the day. He had no rest. The period when he had formerly sought repose, was now made like the day, and all was alike gloom and sadness.
The light is short because of darkness - Margin, near. The meaning is, probably, "even the day has lost its usual brilliancy and cheerfulness, and has become gloomy and sad. It seems to be like night. Neither night nor day is natural to me; the one is restless and full of cares like the usual employments of day, and the other is gloomy, or almost night, where there is no comfort and peace. Day brings to me none of its usual enjoyments. It is short, gloomy, sad, and hastens away, and a distressing and restless night soon comes on."

They change the night into day - These purposes and thoughts are so very gloomy, that they change day into night.
The light is short because of darkness - אור קרוב מפני חשך or karob mippeney choshek, "The light is near from the face of darkness." I have scarcely any light: what is called light is so near akin to darkness, that it is scarcely severed from it. There is either no light, or merely such as is sufficient to render darkness visible. A fine picture of the state of his mind - he was generally in darkness; but had occasional gleams of hope.

They change the (m) night into day: the light [is] short because of darkness.
(m) That is, have brought me sorrow instead of comfort.

They change the night into day,.... Meaning either his friends, by what they had said unto him, or the thoughts of his heart, which comes to the same sense; these being in the night season employed about what had been said to him in the day, insomuch that he could get no sleep, the night was as broad day unto him; or they put the day before the night, contrary to the order of nature, as Noldius (z) observes, whereas the night is before the day, Genesis 1:5; his friends promising him long days, and an age clearer than noon day, as bright as the morning, Job 11:17; when the night of death was coming on, and he was hastening to the dark and silent grave:
the light is short because of darkness; the morning light, or light of the day, when that comes continues but for a short time, because of the darkness of the evening, which quickly follows; or because of the darkness of fiction, which fills it up, and makes it uncomfortable; or the light of prosperity, could it be enjoyed, is but short, because of the darkness of adversity; or "the light is near" (a), as in the original text; though Jarchi interprets the word "short" as we do; Noldius renders it, "the light is rather nearer than darkness" (b); after the night has been spent without sleep, the morning light is nearer than darkness; that may soon be expected, and so an end to sleep and rest.
(z) Ebr. Part. Concord. No. 1931. (a) "propinquam", Pagninus, Montanus; so Junius & Tremellius, Piscator, &c. (b) Ib. p. 642.

They--namely, "my friends."
change the night into day--that is, would try to persuade me of the change of my misery into joy, which is impossible [UMBREIT] (Job 11:17); (but) the light of prosperity (could it be enjoyed) would be short because of the darkness of adversity. Or better for "short," the Hebrew "near"; "and the light of new prosperity should be near in the face of (before) the darkness of death"; that is, they would persuade me that light is near, even though darkness approaches.

They - My thoughts so incessantly pursue and disturb me, that I can no more sleep in the night, than in the day. The light - The day - light, which often gives some comfort to men in misery, seems to be gone as soon as it is begun. Darkness - Because of my grievous pains and torments which follow me by day as well as by night.