HOW DO THE PRESENT, PAST, PRESENT PERFECT, PAST PERFECT TENSES COMPARE?

Can you tell these tenses apart? 

My goal here is to compare the present, past, present perfect and past perfect tenses using a single example sentence.

I imagine you're still having trouble distinguishing between these different tenses. How can you clearly distinguish them without falling into the trap?

The first thing to do when you have sentences of different natures is to go back to their definitions. As you know, tenses apply to a specific period of time, depending on what you want to say. I'd like to illustrate this in a single sentence so you can see the differences between the sentences.

The only sentence to use for my illustration is: working with IBM.

I. SIMPLE PRESENT VS. PRESENT CONTINUOUS 

- I regularly work with IBM on specific assignments = we use the simple present tense to talk about things that happen again and again, it focuses on repeated facts and events. 

- I am currently working in my IBM office = in this situation, the action is taking place now using the present continuous.

Check this out: simple present vs. present continuous: the simple present refers to something that happens over a longer period of time while the present continuous can also refer to something that happens for a limited period of time but is not necessarily happening at the present moment: I am working with IBM on specific assignments this year = she may not be working now but for a limited period of time.

II. SIMPLE PAST VS. PAST CONTINUOUS

- I worked with IBM a year ago = in this situation, we use the simple past to talk about things that happened in a time that is now long gone.

- She was waiting for her daughter to get out of school to pick her up yesterday at 5pm = in this situation, we use the past continuous because the action took place at some point in the past.

Check this out: Past continuous vs. Past simple: I was working at IBM when you spotted me in my office. I was working at IBM (long action in the past tense so we use the past continuous tense), when you spotted me in my office (short action in the past tense, so we use the simple past tense).

III. PRESENT PERFECT SIMPLE VS. PRESENT PERFECT CONTINUOUS

- I have worked at IBM for a few months now / I have worked at IBM since last year = in this case, the present perfect simple is used to talk about the present result of a past action: what matters here is the present result and not the action itself which was the root cause. Note that the action is still in effect, unlike the past action.

Check this out: Simple past vs. Present perfect simple: I worked there for 10 years (the action and result are in the past and completely finished in the present) and I have worked there for 10 years (the result has an impact on the present from a past action).

- I have been working at IBM for 10 years / I have been working at IBM since you got promoted = in this situation, we use the present perfect continuous to talk about an action that has gone on up to the present time.

IV. PAST PERFECT SIMPLE VS. PAST PERFECT CONTINUOUS

- I had already worked for IBM when you joined the company = in this situation, we have an anteriority of the first action, the past perfect simple tense, with respect to the second action in the past: They had already left when I arrived.

- How long had you been waiting for him when she finally arrived? / He was exhausted yesterday afternoon because he had been working since 8 o'clock in the morning = in this situation, we use the past perfect continuous tense to talk about an action that continued until a certain point in the past.

V. PRESENT PERFECT CONTINUOUS VS. PAST PERFECT CONTINUOUS

Compare the present perfect continuous and the past perfect continuous: we have been working flat out so we are going to take a vacation now (the result in the present tense is: take a vacation now); we had been working flat out so we took a vacation yesterday (the result in the past tense was take a vacation then).