I bought a new bike this week, but it has just been stolen.

[Alice Chu]

If today is Friday, is my understanding correct?
1. I bought a new bike this week, but it has just been stolen.
It means I bought a new bike at any time from Monday to the moment before it was stolen. I don’t have the bike now.

2. I have bought a new bike this week. I’ll ride it to the beach tomorrow.
It means I bought a new bike at any time from Monday to the moment before now. I have the bike now.

 

[Yankee]

If today is Friday, is my understanding correct?
1. I bought a new bike this week, but it has just been stolen.
It means I bought a new bike at any time from Monday to the moment before it was stolen. I don’t have the bike now.:tick:

2. I have bought a new bike this week. I’ll ride it to the beach tomorrow. "Have" is not necessary to convey meaning.
It means I bought a new bike at any time from Monday to the moment before now. I have the bike now. :tick:

Y.

 

[emsr2d2]

I think we've said this before but I'll say it again - in general, when talking about one event in the past, don't use the present perfect with a statement of time.

I bought a new bike this week.
I have bought a new bike.

 

[Tdol]

If today is Friday, is my understanding correct?
1. I bought a new bike this week, but it has just been stolen.
It means I bought a new bike at any time from Monday to the moment before it was stolen. I don’t have the bike now.

Yes, but there might be room for a day or two before- we don't necessarily need such scientific precision of it feels like this week, when it was bought last Friday- the frustration is over the very short time you had it before it was stolen.,

 

[5jj]

we don't necessarily need such scientific precision ,

Right.
.
In your determined effort to understand fully the messages conveyed by the uses of the various tenses and aspects, Alice, you are trying to find too much meaning in those tenses and aspects themselves.

The guidelines you find in grammars and course books are just that, guidelines. They are attempts to explain how most native speakers use these forms most of the time. In an attempt to be helpful, some writers give the impression that these guidelines are absolute rules. They are not. If you follow the guidelines, you will probably produce utterances that are nearly always acceptable to native speakers. However, you cannot use these guidelines to work out precisely what message a speaker/writer was attempting to convey. Even if the speaker has a precise idea of timing in mind (and that is not necessarily a given), it is the combination of tense/aspect and full context, often known only to the speaker themself, that conveys that timing, and possible consequences.

Note too, that an utterance such as I have bought a new bike last week, which breaks one of the golden rules about never using a present perfect with a marker of past time, will probably pass unnoticed in speech. The speaker has probably conflated two thoughts, I bought a new bike last week and I have bought a new bike. The person who hears the 'incorrect' utterance will receive the intended message, probably without realising that a teacher might see a mistake.


This thread is about the present perfect, but I'll just note here that many native speakers use the past perfect far less often than many course books suggest we should.

 

[jutfrank]

In my view, you're making the same major mistake over and over again, which is making up your own poor example sentences and then trying to understand what you mean. You're not going to arrive at any deep understanding this way. I really think you should change the kind of questions that you ask us.