Anadverbial clause of time gives temporal characteristics to the action expressed in the main clause. The action of the subordinate clause can be characterized as anterior, simultaneous or prior to that in the principal clause. A time clause can be introduced by the following conjunctions and conjunctive expressions: as, as soon as, as long as, when, whenever, while, now that, till, until, after, before, since, the time (that), the day (that), the moment, the instant, next time, every (each) time, directly, immediately, instantly, once.
The choice of the conjunction is conditioned by the character of the action in the clause: anteriority, priority, simultaneity, succession, repetition, etc.
When a Forsyte was engaged, married, or born, the Forsytes were present. Whenever there was a pause, he gently asked again. (The conjunctions when and whenever introduce clauses expressing repetition.)
As they stood up, Ivory clapped him on the shoulder. (The subordinate clause denotes the moment when the action of the principal clause takes place.)
While he walked around, Christine sat and knitted at a distance. (The predicate in the subordinate clause expresses a durative action, which coincides in time with the action expressed by the predicate in the main clause.)
And now that Cecily had married, she might be having children too. Our hostess, once everyone had arrived, was full of good humour. (In both these cases the predicate in the subordinate clause expresses a completed prior action which fixes the moment from which the action or state expressed in the main clause becomes possible; therefore the subordinate clause of time has a shade of causal meaning.)
As they approached the house, they became quieter and quieter. (Both the actions are gradually developing.)
They were calling each other ‘George’ and 'Elizabeth' before they reached Camden Town. (The subordinate clause points to the moment before which the action of the main clause was in progress. The action of the predicate in the subordinate clause is posterior.)
The heavy guns began again soon after it was light.(The action of the subordinate clause, which is prior, fixes the beginning of the action in the main clause.)
The last time we talked, he said he needed another two days.
The next time I come here, I'm going to be better.(The expressions the first time, the next time, or the third time are used to express a single occurrence of the event expressed by the predicate)
The adverbial clauses in the sentences of the following type are also time clauses:
Scarcely had his hands touched her head, when she sighed deeply.
Hardly had they entered the house, when a violent thunderstorm broke out.
No sooner had I wiped one salt drop from my cheek, than another followed.
The peculiarity of such sentences is that the conjunctions when and than introducing adverbial clauses of time are correlated with the adverbs scarcely, hardly, no sooner in the main clause.
In the clauses introduced by whenever the analytical subjunctive with the mood auxiliary may (might) can be used. In this case these clauses have additional concessive meaning.
Whenever you may (might) come, you are welcome. – Когда бы вы ни пришли, мы вам всегда рады.
It should be born in mind that besides time clauses the conjunction when can introduce subject, predicative, attributive and object clauses.
And people love their homes, even when things are tough.(Clause of time)
The next thing to discover is when the paint was last seen without that smear.(Predicative clause)
Nothing told her when the eyes of her friend were for an instant fixed upon her, when the mind of her friend for a moment wondered at the strange, new look in her face. (Object clause)
There were moments when I felt all the misery of my friendlessness, all the peril of my dreadful responsibility.(Attributive relative clause)
Adverbial clauses of time introduced by the subordinating conjunction while should not be confused with independent clauses introduced by the coordinating conjunction while.
There was a pause while he raised his cup and drank some tea. (Clause of time)
His face was disturbed and troubled,while his clothes were disarranged and untidy.(Adversative coordination)