Learn English – “First thing I did” vs “First thing I have done”

grammar

What is the difference between the simple past and present perfect in the following?

When I first got here, I bought a car. [Assuming I still own the car]. This is the first thing I have done.

When I first got here, I bought a car. [Assuming I still own the car]. This is the first thing I did.

Best Answer

The clause when I first got here is an expression of finished time (cf. yesterday, last week), and requires the past simple. So your first sentence in ungrammatical. If, on the other hand, you use an expression of unfinished time, you usually use the present perfect:

Since I first got here, I have bought a new car, found a job, got married, etc.

The difference is between the words when (finished time - past simple) and since (unfinished time - present perfect).