V-ed vs have + p.p.
RuleUse the simple past for finished time (yesterday, ago, in 2019); use the present perfect for time connected to now (today, already, so far).
Curiosity
"I lost my keys" and "I have lost my keys" are both correct, yet they feel different. What changes?
Intuition
The simple past is a closed event at a finished time. The present perfect means the event still matters now (you still cannot find the keys). The time marker decides.
Visualization
On the timeline, see the same event two ways: as a closed past point (simple past) versus reaching to now (present perfect).
The time marker decides: finished past vs connected to now.
NOW
visited in 2018
finished time → simple past
Essence
Finished-time markers (yesterday, last week, ago, in 2020) force the simple past. Now-connected markers (today, this week, already, yet, recently, so far) call for the present perfect. On the TOEIC, read the time adverb first.
Examples
I visited the headquarters in 2018.
I have visited the headquarters twice so far.
The supplier raised its prices last month.
Mini-quiz
"The shipment ___ last Friday." Which fits the blank?