‘The train leaves soon.’
‘The train will leave at nine.’
2. Languages in which the form of the verb itself changes to express futurity are said to have future tenses. Some grammarians describe ‘will/shall’ as markers of the future tense; however, there are various ways of indicating futurity in English, e.g. ‘They will arrive next week’, ‘They’re going to arrive next week’, ‘They’re arriving next week’, or simply ‘They arrive next week’. Formally, ‘will’ and ‘shall’ behave like other modal auxiliary verbs, and so here they have been classified under modality rather than tense.
3. In English, then, tense often anchors an event to present or past time. However, present tense combined with simple aspect also expresses plain, ‘timeless’ facts (‘The world is round’), and habitual actions (‘She jogs every morning’).
4. Note that a change of tense is normally required in reported or indirect speech. ‘"It’s absurd," he said’ becomes ‘He said that it was absurd’.