Use the Present Perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, at that moment, that day, one day, etc. We CAN use the Present Perfect with unspecific expressions such as: ever, never, once, many times, several times, before, so far, already, yet, etc. 


she has cookek some sweets cakes for a few days.

Sometimes, it has been pretty cold an after a couple of days we've had spring temperatures.