The category of tense finds different interpretations with different scholars.
According to one view, there are only two tenses in English: past and present. Most British scholars do not recognize the existence of future.
In traditional linguistics grammatical time is often represented as a three-form category consisting of the “linear” past, present and future forms. The meaning of the category of tense is the relation of the action expressed by a finite verb to the moment of speaking.
According to the concept worked out by Prof. Blokh, there exist two tense categories in English. The first one – the category of primary time – expresses a direct retrospective evaluation of the time of the process denoted. It is based upon the opposition of past vs. present, the past tense being its strong member. The second one – the category of “prospective time” – is based on the opposition of “after-action” and “non-after-action”, the marked member being the future tense.