I am learning Reported Speech in the Past now. In my English textbook there is a rule: "When it is provided when exactly the action happened, you can leave the Past Simple as it is". I was looking it up on the internet, but I haven't found anything related to this yet. So, do I need to write an action with specified time in the Past Simple or do I need to use the rules to write actions in the Reported Speech? For example, do I need to write
- He said that he finished writing the letter at 9 o'clock yesterday
or
- He said that he had finished writing the letter at 9 o'clock yesterday ?