"The term 'tense' would seem to be the least understood term in linguistics. It does not, and cannot, indicate the time setting of the verb because it only means something when compared to the time setting the verb relates to. 

 There are only two tenses, 'the past' and 'the non-past'. Tense is solely chosen by the speaker. Verbs relate to either 'the past' or the 'non-past'. This is solely determined from the context. (Perfect verbs relate to the time period that follows the one in which the actions or states occur. Imperfect verbs relate to the same time period.) The time periods 'past of the past' and 'past' occur in the 'past' time zone. The 'present' and 'future' time periods occur in the 'non-past' time zone.  

 If the tense matches the time zone, the verb is 'natural'. If they do not match, then the verb is 'unnatural'. Natural verbs can be taken at face value. Unnatural verbs require deeper analysis. An unnatural verb in the past tense is either hypothetical or is informing the listener that the speaker is less friendly than usual. An unnatural verb in the present tense informs the listener that the speaker is more friendly than usual. 

 In English teaching there is a structure described as a third conditional. All text books describe this as an hypothetical event in the past and all text books are wrong to do so. If the actions described by the verbs occur in the past of the past, then it is as likely that the condition has been met as it is that the condition in a first conditional (e.g. ""If it rains, we will get wet."") will be met. Only third conditionals whose verbs relate to the non-past time zone are hypothetical. 

 That traditional grammar descriptions of tense are wrong can be easily seen from a line in a Bob Seger song, ""I wish I did not know now what I did not know then"". Traditional grammar describes both verbs as being 'past simple'. Yet they cannot have the same description because they have different meanings. They are more correctly descibed as 'non-past simple in the past tense' and 'past simple in the past tense' respectively.   Mel Tisdale"