The duration of the action in Othello is constrained by opposing requirements. The pace and tension of events is considerably enhanced by the impression that everything takes place very quickly—too quickly to allow the deceived and innocent time to clarify the truth of the situation, too quickly to permit Iago's plotting to be detected. However, in order that the events referred to, and the deterioration of Othello's character, achieve plausibility, it is necessary to present the passage of some considerable time. Thus the playwright's use of 'double time'.
The first act of the play is packed with incident. Desdemona and Othello are married, but only just married—if she had been absent from her father's house for more than a matter of hours, he would surely have noticed! Indeed, they are so newly married that it does not appear they have time to consummate the match before being parted: Iago makes much of the idea that the pair are in bed together, but this seems to be primarily with the idea of enraging Brabantio—at which he is most successful. So Brabantio storms into a confrontation with Othello, and on to an audience with the duke. Immediately after Brabantio's accusations have been proved false, Othello is ordered to Cyprus, and as he has to leave very quickly, there does not seem to be much time left for his wife. Desdemona's brief protest ("Tonight, my lord?" I.3.279) would seem to carry an implication of "But it's my wedding night".
However, at the same time that events are moving forward at a great pace, we are also learning about the sequence of events leading to this point. We discover that Othello has not just run off with Desdemona, but had a reasonable period in which to pay her oblique court.
"Her father loved me, oft invited me, he says (I.3.129) and he had time to expound upon the details of this life. It is similarly clear that his visits to Brabantio's house were repeated, by the description of Desdemona being drawn away from his tales by her household duties, and returning to listen more. Othello "oft did beguile her of her tears". (I.3.157)
Similarly, Othello has had time to establish himself in the estimation of the men of Venice. He has promoted Cassio over Iago, and has been around long enough for Iago to suspect him of bedding Iago's wife. All this kind of background information establishes the characters; at the same time it prepares the audience to receive long-term information via the accounts the characters give.
Act Two opens in Cyprus, so clearly some time has passed, but there has been no opportunity for any of the relationships to progress. Othello and Desdemona have been separated, likewise Cassio. Perhaps Iago and Desdemona have become better acquainted, but Iago has not yet been able to further his schemes. So in effect, the action takes up from more or less the point at which the first act ended, at any rate, once the principals have been reunited.
Iago often presents an impression of time passing in his speeches. He anticipates what will happen; for instance, he anticipates that Desdemona's love for the Moor will not last, and expects her to seek new lovers. This almost feels like a kind of sleight-of-hand, stretching the audience's perceptions into the future. Then we are brought back to the present, in which Othello and his wife have at last gone to bed to consummate their marriage. Again, Iago 'prophesies' what he intends to do—firstly, he will make Cassio drunk, later, he will poison Othello's mind against his wife by saying she pleads for Cassio because he is her lover. This seems to stretch out the action itself, so that it does not appear quite so abrupt as it might otherwise seem.
The opening of the third act—Iago enquiring whether Cassio had been a-bed, Cassio replying in the negative—appears to follow on immediately from the action of the second. However, there is theoretical scope for a break here, and greater time might have elapsed. After all, in scene 3, Othello asks whether it is not Cassio who is leaving his house. Iago replies
"Cassio, my lord? no, sure, I cannot think it
That he would steal away so guilty-like
Seeing you coming." III.3.37-39
Iago is being more than a bit disingenuous here, if there has been no break in the action! A man who has just been stripped of his post in embarrassing circumstances would have every reason to sneak out of sight of his former commander—whereas if there has been some time for matters to simmer down, Cassio slinking off is less easy to explain. (Of course, Iago's actual motives are leading him to present Cassio in the worst possible light, but he does not mean to make this obvious to Othello.)
Perhaps more convincing arguments for the passage of time at some point just before or during this act occur when the women speak. Emilia, referring to Desdemona's handkerchief, says:
"My wayward husband hath a hundred times
Wooed me to steal it..." III.3.296-7
If everything has been happening from hour to hour, Iago can barely have had time to mention the handkerchief! Instead, we are given to understand that he has had in mind a scheme concerning it for... and indeterminate period, but certainly more than hours.
Emilia is more precise, reproaching Cassio in the next scene for keeping away from her for a whole lonely week. Thus Shakespeare is stretching out the time frame for the play. And Iago's cunning lie:
"I lay with Cassio lately"
certainly implies that more time has passed than we have actually seen—otherwise Cassio has not been to bed!
The arrival, early in Act Four, of a greeting from Venice, undoubtedly means that time has passed. Such a message would take several days to arrive—this kind of delay would be perfectly understood by contemporary audiences—and it would be absurd for Venice to recall Othello only a couple of days after his arrival in Cyprus, in any case.
In the second scene, Desdemona tells Emilia to
"Lay on my bed my wedding sheets" IV.2.106
In 'short time', these were only used on the previous night, but plainly Desdemona's desire to remind Othello of their earlier passion references a longer interval than this. What we are seeing now appears to be a series of events which follow each other directly on an emotional time-line, but are drawn out more logically in duration, which is explained by these increasing references. Yet because the action drives forward in a single line, Shakespeare retains the sense of doom and inevitability, as well as hiding from his audience the implausibilities of the situation.
By the time we reach Act Five, time seems to have been stretched even more, at least in Othello's mind. he says that Desdemona
"...hath with Cassio the act of shame
A thousand times committed." V.2.209-10
Certainly, his jealousy is exaggerating his wife's supposed betrayal (if Cassio was on a par with Casanova he might have managed this in a few months!), but we must certainly understand that this is not in fact only a day or two after Othello's wedding night. It does seem that Desdemona's infidelities are supposed to have happened since her marriage, rather than before it, as I can hardly imagine Othello would have failed to notice if his new wife had not been a virgin. Presumably he would have mentioned it!
Throughout the play, events follow a swift and direct course—there is no subplot, for everything is directed by Iago and aimed at his goal of revenging himself on Othello. All the action we see is part of the single line of this plot. Whether events actually happen within a few days (excluding the voyage to Cyprus) or over a more extended period is in some ways irrelevant, as we are shown only the parts of Othello's, Desdemona's and Iago's lives which are affected by this emotional progression.
In fact, both the 'short time' and the 'long time' are necessary to the plausibility both of the action and of the deterioration in Othello's character. it is clear that Othello and Desdemona have not had enough time to achieve a real understanding of one another's characters. If they had, she would not be so bewildered by his unexpected rage, and he would not be so easily persuaded of her duplicity. Contrariwise, Othello's essential nobility of character is presented to us as fact—even Iago acknowledges it—and we see in his calm, dignified behaviour in the face of Brabantio's accusations and Cassio's drunken riot, that he does deserve the praise he receives. it is therefore necessary that we do not see him change from a noble general into a passion-filled murderer over the course of three days. Similarly, it is necessary for us to believe that Iago's plots come to fruition with some rapidity—for could his malignity really be kept so well hidden for months? There are plenty of opportunities for his plots to misfire and reveal his essential malice. Yet the suspicions he plants in Othello's mind would be ludicrous in 'short time'.
The balancing of the short and long time scales within this play is so expertly done that it is hard to believe any audience would realise what is happening. There are few direct references to the passage of time within the action (excepting physical changes such as the move to Cyprus), instead the 'long time' is implied by such references as 'an hundred times', 'a thousand times', etc. As the play progresses, it is as though the history of the prior scenes is being subtly revised in retrospect, to allow character development (or rather, deterioration) and to enhance plausibility—in the same way that Iago is revising history for his own ends. Finally, there is murder, denunciation and suicide, and the disparate time schemes have melded together for the culmination of the tragedy.