Two- Present and Past Tense. If you consider aspect, you get perfect (have written, has ignored, had seen), progressive (is growing, was thinking) and perfect progressive (have been talking, had been waiting). Add modals in, you get verb phrases like 'will go' and 'shall go', which is what people refer to as the 'simple future tense'. Notice that you combine a modal verb (will) with a main verb in its present tense (go) to mark future time in a verb phrase. There is no such thing as a 'future tense' in English. Then, there is also voice- active and passive. For passive, you get verb phrases like 'are delighted', 'was given' etc. You can combine voice and aspect together and get phrases like 'has been jailed', 'had been jailed', 'is being jailed', 'was being jailed' If you combine modals with aspect, you get verb phrases like 'may have come', 'will be coming' and if you combine modals with passive voice, you get a phrase like 'would be thrown'.

Two! Past and Non-Past

I know 12!

How much do you want to confuse yourself? ;) Capriccioso has given a great answer: fundamentally, you have two tenses (past and present), which are used as the basis to create all the other forms. Yes, the future "tense" is constructed out of other forms, and doesn't exist insofar as the verb itself isn't really conjugated. I find the longer lists of 12, 16, etc etc, although used in textbooks, are both daunting and confusing. Really, you get these divisions based on how the textbook writer wishes to divide up and classify the forms.

I can agree with Eliot or even britishcouncil.org, which says 'There are two tenses in English – past and present.'