Back shifting of tense etc

Dear forum users

I would like your critical comments (including from non native users).

The two statements that have led me to open this new thread for a meaningful discussion are:

You will appreciate that in order to ensure uniformity and to avoid distortion in communication we need to be aware of the common yardstick with which we can assess the acceptability of how sentences are (are to be) used in formal and informal contexts. Informally, even chat language is permissible depending on the persons concerned. Here not much grammar is adhered to. Formally, the situation becomes different and we need to be using the globally comprehensible/acceptable language. So is the position when students/candidates are tested for their proficiency in the language.

So, formally, while reporting a direct speech we consider the nature of sentences used by the speaker as well as the time and place at which they were spoken. Accordingly, with due regard to the ‘reporting verb’, the need for the application of grammar becomes indispensable.

Usually, we do not change any word of the direct speech in the following cases:

  1. My teacher said that honesty is the best policy. (Proverbial saying)
  2. Uncle Sam said that the strong always dominate the weak. (Universal truth)
  3. Our professor said that water consists of hydrogen and oxygen. (Scientific fact)
  4. The minister said that his country became independent in 1900. (Historical occurrence)
  5. He said that he is a tutor in a university. (Continuing state)

Now, when we are not sure of the context, we need to be neutral and treat the speech as remote.

What has already triggered a discussion is this sentence below, which I would like to analyse in detail assuming that the week starts on the 1st of March as shown within parentheses:

“The exhibition finished last week,” explained Ann. (Stated on March 08)

Ann explained that the exhibition finished last week. (Reported between March 8 and 14)

Ann explained that the exhibition had finished the week before the last. (Reported between March 15 and 21)

Ann explained that the exhibition had finished the preceding week. (Reported on March 22 or later)

======

She said: I am coming tonight. (Stated on April 01, perhaps earlier on the day)

She said she is/was coming tonight. (Reported on April 1st, later on the same day)

She said she was coming last night. (Reported on April 2nd)

She said she was coming the night before the last. (Reported on April 3rd)

She said she was coming that night. (Reported on April 4th or later)

(This is how I have understood the situation. In our language back shifting is possible for adverbs, particularly of time.)

I thank you all for not disagreeing with me.