The verb phrase is the primary grammatical element where time distinctions are expressed. It indicates, for example, whether an event took place in the past, present, or future. However, there is no one-to-one match between the tense of a verb phrase and the time it refers to.
Moreover, there are only two tense forms of verbs in English, namely the present tense form and the past tense form. To express future time in English, a combination of auxiliary verbs and main verbs are typically required.
When discussing the expression of time in the verb phrase, it is necessary to uphold a distinction between grammatical forms, e.g. present and past tense, and the real-world notion time. Thus, although English verb phrases have only two tenses - present or past - they can also refer to the future, and, in addition, they can offer a variety of temporal perspectives on events and states.
In this section the focus is on the expression of past, present and future time. The first two are dealt with rather summarily here. For more detailed discussion follow the links below.
Referring to the present
The simplest forms of verb phrases used to refer to present time are those that consist only of a main verb in the present tense, as in the following examples.
(1) We expect the results from our experiment to match the theoretical assumptions rather closely.
(2) On an average an elephant weighs about five tons.
(3) We agree with Smith that the concept of innate constraints is inherently problematic.
(4) As part of the ritual, the men gather in the centre of the village and rub themselves with leaves of the acanthus plant.
Verbs that normally occur in the simple present (and not in the present progressive) denote present states or encode other permanent characteristics. Also, reference to habits and recurring events is typically made using the simple present tense. Verbs that most often occur in the simple present tense include:
Verbs denoting sensory perception: hear, detect, smell, taste, etc.
Verbs denoting mental attitudes: agree, appreciate, doubt, hope, imagine, suppose, etc.
Verbs denoting ownership, inclusion, and similar relations: have, own, possess, belong to, consist of, comprise, etc.
The simple present tense alternates with the present progressive to refer to present time. Also, verb phrases with modal auxiliaries in the present tense are used to refer to present time. See the following links:
Referring to the past
The simplest verb phrases referring to past time consist only of a verb in the past tense. The past tense firmly anchors a past state, event, etc. at some definite time in the past, or in some definite period in the past.
(5) The train for London left at 3 o'clock.
(6) Miss Redfurn lived as a spinster all her life.
The simple past tense alternates, for instance, with the present perfect, which is used to refer to states, events, etc. that bear relevance to present time, although they may have occurred or merely started in the past. See the following link for discussion.
Referring to the future
Since English has no future tense form of verbs, various types of expressions are used to talk about states, events, etc, that belong to future time.
The most common types of verb phrases with future reference occur with the modal auxiliary will as the first verb. The meaning is that of a neutral prediction about the future. The use of will normally indicates a fairly high degree of certainty about the future, as in the following examples:
(7) The number of senior citizens will continue to rise.
(8) The Committee will meet again on Tuesday at 8 o'clock.
Main clauses with will are often accompanied by dependent clauses (in italics in the examples below) or other expressions specifying conditions for the prediction:
(9) If many people lose their homes, the real estate market will deteriorate.
(10) If the result of a previous test is available, the lab will be able to compare the results and form better conclusions.
A similar use of will occurs in some kinds of statements about general truths, especially ones that resemble conditional statements. This use of will alternates with the simple present tense.
(11) Aluminum melts at 1220 degrees Fahrenheit.
(12) Aluminum will melt at 1220 degrees Fahrenheit. (Cf.: Aluminum will melt if heated to 1220 degrees Fahrenheit.)
be going to
In spoken English, the so called semi-modal be going to is the second most frequent way of referring to the future. However, in academic prose, its use is fairly restricted. One reason for this is that it commonly denotes the future fulfilment of somebody's intention, as in the following examples:
(13) My son just talks me to death telling me what he is going to do.
(14) The government are going to publish a draft bill in April.
Obviously, if the subject matter is such that the intentions of individuals are relevant the be going to construction can be used, but there are also more formal ways of referring to intentions, as in the following examples:
(15) In the following chapters I intend to propose a theory of mind.
(16) This chapter aims to propose a theory of narrative structure.
Be going to is also used to denote the future fulfilment of present circumstances. Again, this use is frequent in spoken varieties, but rare in formal writing. The following examples illustrate this use:
(17) All the statistics indicate that production is going to increase.
(18) Demographic trends show that each taxpayer is going to support significantly more beneficiaries than today.
In such cases, will can frequently be used without a significant change in meaning.
The present progressive and the simple present tense
Like be going to, the present progressive (BE+the ing- form) is anchored in the present, namely through the existence of a program or arrangement about the future. The following examples illustrate this use:
(19) We are leaving early tomorrow morning.
(20) I am taking my mother out to dinner tonight.
The simple present tense can also be used with future reference, with a strong sense of inevitability. The following examples illustrate statements about the calendar, predictable natural phenomena, and formally scheduled events, respectively.
(21) Tomorrow is Friday.
(22) When is the next full moon?
(23) The tournament starts next Wednesday.
In main clauses, the use of the present tense with future reference alternates with explicit markers like will. However, there are cases where the simple present tense is obligatorily used. The most important ones are dependent clauses with temporal or conditional meaning. The following examples illustrate this use.
(24) Europe's air quality will improve if all member states decide to comply with the Kyoto protocol.
Here, the decision to comply with the Kyoto protocol lies in the future, as does the improvement of Europe's air quality. In the main clause, will is used to mark reference to the future, but in the dependent clause - the conditional if-clause - the simple present tense is used.
(25) According to this view, the ultimate fulfilment of the prophecy will occur when the Messiah returns.
Again, the reference to the future in the main clause is made by the use of will, whereas the temporal dependent clause, the when-clause, has the simple present tense.
Note that the use of the present tense in these two types of dependent clause (i.e. conditional and temporal ones) is not conditioned by the fact that the main clause already marks the future (by will, in our examples). In the following example, with a dependent clause expressing reason (the since-clause), both the main clause and the dependent clause must be marked for the future, and in neither would it be possible to use the simple present tense.
(26) In the future, there will be no thieves, since everyone will be provided with the necessities of life.