Take a different look at grammar with our Present Perfect timeline based on our cartoon story. USE THE TIMELINE. It should really help you understand the grammar. There are explanations below to explain why we use Present perfect and not past simple in the sentences... So, what do these sentences really mean...? 1. I haven't bought lemonade since 2003. 2.I haven't tasted sweet lemonade for almost 10 years! There is a continuing period of time from 2003 up to now, where he did not drink any lemonade. He is thinking about the past and the present together. If he was only thinking about the past (and NOT THINKING ABOUT THE PRESENT AT THE SAME TIME) he would say... PAST SIMPLE: I drank lemonade in 2003 (This is a finished action that is not connected to the present time. He drank that lemonade and it exists no more) Compare with.... PRESENT PERFECT: I haven't bought lemonade since 2003. (He is thinking about all the time from 2003 until now, 2012). Look at the grammar timeline to help you understand this period of unbroken time from 2003 to the present time.
PRESENT PERFECT TIMELINE
Drag your mouse over the dots on the timeline, click on the bubbles that appear and read the descriptions. You can see from the pictures on the timeline that there is an unbroken, continuing period of time from the middle of 2003 until the end of the timeline where he did not drink any lemonade. It is an action (or actually it is a non-action) from the past that continues up until the present moment now.