Thank you, Writeacher. Can you please have a look at the following sentences?

1) I think in American English you can say: She said she was leaving the hotel the day after (instead of the following day).
2) He said he had lost his keys the night before.
3) I heard him play the piano (is it a mistake, is only "playing" possible?)
4) I saw him get into the car. (is "getting" a mistake?)

1. You'd need to indicate "the day after" what??

... the day after I last saw her.
... the day after the conference.
... the day after we had lunch together.
or what??

2. OK

3. play or playing -- either is fine.

4. get or getting -- either is fine.

1) Yes, in American English, you can say "She said she was leaving the hotel the day after" instead of "the following day." Both phrases convey the same meaning. The phrase "the following day" refers to the day that comes immediately after the one being discussed. However, saying "the day after" has the same effect, indicating that the departure will occur on the day following the current reference point.

2) The sentence "He said he had lost his keys the night before" is grammatically correct. The phrase "the night before" means the previous night. In this context, it implies that the person spoke about losing the keys on the night that occurred prior to the conversation.

3) The sentence "I heard him play the piano" is grammatically correct. The word "play" can be used as both a transitive and intransitive verb. In this case, it is used as an intransitive verb, meaning that it does not require a direct object. Therefore, saying "I heard him playing the piano" would also be grammatically correct.

4) The sentence "I saw him get into the car" is grammatically correct. The verb "get" can be used to describe an action of entering or boarding a vehicle. Thus, using "getting" in this context is not a mistake. Saying "I saw him getting into the car" would also convey the same meaning. Both forms are acceptable.