About “Ago”
When we use “ago,” we must use the past tense. This is what your grammar teacher told you. Here are a few sentences that you might find confusing.
I have been using this computer since three years ago.
She had done her homework two hours ago.
They should have started using it years ago.
All the above sentences use perfect tense with “ago,” and they are all correct. Why? Well, the first sentence is correct because “since” is used. When we use “since,” we use the perfect tense. When we use both “since” and “ago” in a sentence, “since” is a bigger brother, and we obey the bigger brother. The second sentence is in perfect tense, but it’s past perfect. To be more accurate, “ago” cannot be used with the present perfect tense, but the past perfect tense is okay. In the third sentence, “should” is a modal verb which has no past form. When we need to express something happened in the past, we have to use “should + perfect tense” form.
“Ago” is used with the past tense, and above are just a few exceptions.
- Ron Lee