How to define the future and the past?

In the initiative post I have said this:
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If past time is "before now", we find that most present actions have started "before now":
Ex: He teaches in school.
He doesn't teach just by the time we use Simple Present to say it. He has started it a long time "before now". Therefore, "before now" is not the definition of the past time. Then how to define the past time?
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I admit past time is "before now", but the example "He teaches in school" renders the definition not to be "before now". There is a trick there. What is it? If you know, you may play it with your friends :-)

The only use of 'initiaitive' in current American English is as a noun. It is never used as an adjective. I was surprised to see it in the dictionary as an adjective, since I have never seen it used that way before.

Thank you D,

As I said, I know very little English. And I type instantly. I am sure there are some other mistakes I was not aware of.

Explanation of English tense is mainly for foreign students who depend largely on grammars, rather than experience. They use English sometimes, but not too often. English native speakers don't even need it. One can grow up in an English speaking country and speak fluently and correctly without any learning. This is, I humbly and widely guess, why they didn't spend time in updating the logic in explanation. They have kept a lot of babble there untreated. As a foreign learner of English, I would like to see a more reasonable way of explaining tense.

Because grammar writers hide away the Past Family (adverbials in the pattern of "in the past xx years"), they don't even define to us what is "definite past time adverbials". They may collect some few for you: yesterday, last week, five years ago, etc. This is their best collection. Why didn't they make a whole collection of them? No, they will never, because they don't want you to see the Past Family.

Either in books or on the web, no one will find a grammar reference that has linked to the Past Family, or made a wholesome collection of the definite past time adverbials. Foreign students have to do it yourself.

Like German, and maybe other Germanic languages (but unlike the Romance languages) English doesn't have a future tense.

The name doesn't matter at all. The modal verbs are used to denote the future, if you can define what the future time is. Please correct me if you are kind enough.

Every grammar book or website doesn't talk about the pattern of "in the past xx years". Does it prove that the pattern doesn't exist?

i think 'Time' consists of three types:

1. past
2. present
3. future

the tense consists of two types only(T.G.G):

1. past
2. present

"i think 'Time' consists of three types:

1. past
2. present
3. future

the tense consists of two types only(T.G.G):

1. past
2. present"

If you are specifically talking about English, I would agree with you.